Anatomy and Pathology of the Cerebellar Peduncle - asnr. · PDF fileof the upper brains tem...
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Anatomy and Pathology of the Anatomy and Pathology of the Cerebellar Cerebellar Peduncle Peduncle Toshio Moritani MD, PhD, Akio Hiwatashi MD, Henry Z Wang MD, PhD, Yuji Toshio Moritani MD, PhD, Akio Hiwatashi MD, Henry Z Wang MD, PhD, Yuji Numaguchi Numaguchi, MD, PhD, Leena Ketonen MD, PhD, Sven E Ekholm , MD, PhD, Leena Ketonen MD, PhD, Sven E Ekholm MD,PhD MD,PhD, Per-Lennart A Westesson MD, PhD, DDS , Per-Lennart A Westesson MD, PhD, DDS Division of Diagnostic and Interventional Neuroradiology, Department of Radiology, University of Rochester Medical Center, Rochester NY Division of Diagnostic and Interventional Neuroradiology, Department of Radiology, University of Rochester Medical Center, Rochester NY F F E-mail: [email protected] E-mail: [email protected] Infarction Infarction (Figures 2-5) The inferior cerebellar peduncle is mainly supplied by the posterior inferior cerebellar artery (PICA). The middle cerebellar peduncle is supplied by the anterior inferior cerebellar artery (AICA) and partly by the superior cerebellar artery (SCA). The superior cerebellar peduncle is mainly supplied by the SCA. These arteries vary greatly in origin, size, course, and supply area, the aera of infarction are variable in extent and location, ranging from a small infarct localized into the cerebellar peduncle (Figure 2 and 3) to la rge involvement of the cerebella r hemisphere, and can be associated with the involvement of pons, midbrain, thalamus and occipital lobe (Figure 4) (4). Bilateral AICA territory infarcts are very rare (Figure 5), and can occur due to hypoperfusion in the watershed area between the AI CA and the SCA (6). Wallerian degeneration of the pontocerebellar tracts Wallerian degeneration of the pontocerebellar tracts secondary to pontine hemorrhage or infarction secondary to pontine hemorrhage or infarction (Figure 6). Wallerian degeneration secondary to pontine hemorrhage or infarction is usually bilateral. Differentiating from infarction is important. This is because of damage to both ipsilateral pontine nuclei (which deliver axons to the contralateral cerebellar hemisphere) and the ipsilateral axons (which originate from the contralateral pontine nuclei and course into the ipsilateral cerebellar hemisphere) (Figure 6G) (3). The T2 prolongations were first recognized from 26 days to 4.5 months after insult Theoretically, the wallerian degeneration of the pontocerebellar tracts should extend out to the mossy fibers in the cerebellar cortex, as seen on the pathological specimen; however this is beyond the resolution of MRI(3). Hypertrophic olivary degeneration occasionally coexists with these lesions, because the lesion can also involve the area in the Guillain-Mollaret triangle (Figure 6H) (7). Figure 3. An infarct in the inferior cerebellar peduncle. 57- year-old man with ataxia and diplopia. A,B. T2WI and DWI at 24 hrs after onset clearly reveal homogenous round hyperintensity areas representing acute infarcts in the bilateral middle cerebellar peduncles and both cerebellar hemispheres. A, B, FLAIR image and DWI show a hyperintense lesion, representing a small acute infarct in the left inferior cerebellar peduncle. Figure 5. Bilateral infarcts in the middle cerebellar peduncle. 80- year-old man with ataxia and vertigo. A B A B G. Cerebellar connections. The cortico-ponto-cerebellar pathway (corticopontine tract and pontocerebellar tract) is major afferent fibers through the middle cerebellar peduncle. Olivocerebellar fibers (afferent fibers) are through the inferior cerebellar peduncle. Efferent fibers mainly arise from the dentate nucleus to the red nucleus through the superior cerebellar peduncle (cerebello-rubro-thalamic tract). Osmotic Osmotic myelinolysis myelinolysis (Figure 7). Symmetrical lesions in bilateral middle cerebellar peduncles without central pontine myelinolysis (CPM) was reported as cerebellar peduncle myelinolysis (8). However, in our case, bilateral cerebellar peduncle lesions accompanied by CPM (Figure 7). These lesions are presumed to be due to myelinolysis itself or secondary degeneration related to CPM. Figure 6. Wallerian degeneraion in the middle cerebellar peduncle. 50-year-old man with quadriparesis and loss of co nsciousness after chiropract ic. F. On the pathological specimen of another patient, wallerian degeneration of the pontocerebellar tracts is recognized as symmetric rounded lesions (arrows) in bilateral middle cerebellar peduncles and extends out to the mossy fibers in the cerebellar cortex (open arrows) (Ref. 3. Int J Neuroradiol 1998;4:171-177. Toshihiro O'uchi MD with permission). A, B. DWI and T2WI shows hyperintense lesions in the right cerebellar hemisphere and the left side of the pons at 10 days after onset, which represents subacute hemorrhagic infarcts. C, D. On follow-up MRI at 8 months after onset, old infarcts show very high intensity on T2WI and low intensity on FLAIR image as CSF. Symmetrical round hyperintense lesions in bilateral middle cerebellar peduncles are seen on T2WI and FLAIR image (arrows). These lesions represent wallerian degeneration of the pontocerebellar tracts secondary to pontine infarction. E. T2WI at the level of the medulla demonstrates symmetric hyperintense lesions corresponding to the bilateral olivary nuclei, representing hypertrophic olivary degeneration (arrows). A B F G. Wallerian degeneration in bilateral middle cerebellar peduncles The lesion involving the pontine nucleus can also involve the ponto- cerebellar tract from the contralateral pontine nucleus, which results in wallerian degeneration in bilateral middle cerebellar peduncles. C D E A. B. T2WI shows a hyperintense lesion in the central pons representing CPM. T2WI also shows symmetrical round lesions in the bilateral middle cerebellar peduncles (arrows). These lesions maybe due to myelinolysis itself or secondary degeneration. Figure 7. CPM 50-year-old female presenting with loss of consciousness after rapid correction of hyponatremia. A B Neurofibromatosis Neurofibromatosis (Figure 19) (Figure 19) Hamarto matous lesions are obse rved in 80% of all patien ts with neurofibromatosis type 1. Multiple lesions in the basal ganglia, optic radiation, brainstem, and cerebellar peduncles are common (Figure 19). Pathologically, these lesions are foci of hyperplastic or dysplastic glial proliferation and considered malformations rather than neoplasms. Diffuse axonal injury (DAI) Diffuse axonal injury (DAI) (Figure 20) (Figure 20) The gray-white matter interface, the corpus callosum, and dorsal aspect of the upper brainstem including the superior cerebellar peduncle are three specific areas for the occurrence of DAI. Other less frequent locations include the caudate nuclei, thalamus and internal capsule. Cerebellar involvement including the middle cerebellar peduncle is uncommon (Figure 20). Tumor Tumor (Figures 17 and 18). Benign tumors such as astrocytoma or cavernous angioma can involve in the cerebellar peduncle (Figures 17). An extra-axial tumor such as benign acoustic schwannoma occasionally displaces the middle cerebellar peduncle (Figure 18). Malignant tumors such as metastasis or glioblastoma multifo rme also o ccu r in t he cerebellar peduncle. Tumors involving the ventricular portion or the cerebellar portion of the middle cerebellar peduncle can be removed by surgery (3). A. FLAIR image shows a hyperintense lesion in the left middle cerebellar peduncle to cerebellar hemisphere due to DAI. B. DWI shows hyperintense lesions in the corpus callosum and bilateral internal capsules, which is typical findings of DAI. Figure 20. DAI. 29-year-old woman with DAI, presenting with loss of consciousness after motor vehicle accident. A B A,B T2WI and FLAIR image show multiple asymmetric lesions in the pons, middle and inferior cerebellar peduncles, and cerebellum. Figure 19. Neurofibromatosis type 1. 4-year-old girl presenting with developmental delay. A B Re feren ces 1) Carpenter MB. Cerebellum. In, Core Textbook of Neuroanatomy. 5th edition. Baltimore, MD: Williams &Wilkins, 1996;583-623. 2) Tomita T. Surgical management of cerebellar peduncle lesions in children. Neurosugery 1986;18:568-575. 3) O'uchi T. Wallerian degeneration of pontocerebellar tracts after pontine hemorrhage. Int J Neuroradiol 1998;4:171-177. 4) Amenco P, Rosengart A, DeWitt D, Pessin MS, Caplan LR. Anterior inferior cerebellar artery teritory infarcts. Mechanisms and clinical features. Arch Neurol 1993;50:154-161. 5) Milandre L, Rumeau C, Sangla I, Peretti P, Khalil R. Infarction in the territory of the anterior inferior cerebellar artery: report of five cases. Neuroradiology 1992;34:500-503. 6) Akiyama K, Takizawa S, Tokuoka K, Ohnuki Y, Kobayashi N, Shinohara Y.Bilateral middle cerebellar peduncle infarction caused by traumatic vertebral artery dissection. Neurology 2001;56:693-694. 7) Kitajima M, Korogi Y, Shimomura O, Sakamoto Y, Hirai T, Miyayama H, Takahashi M.Hypertrophic olivary degeneration: MR imaging and pathologic findings. Radiology 1994;192:539-543. 8) Mangat KS, Sherlala K. Cerebellar peduncle myelinolysis: case report. Neuroradiology 2002;44:768-769. 9) Aydin K, Sencer S, Demir T, Ogel K, Tunaci A, Minareci O.Cranial MR findings in chronic toluene abuse by inhalation. AJNR Am J Neuroradiol 2002;23:1173-1179. 10) Uchino A, Kato A, Yuzuriha T, Takashima Y, Heijima S, Murakami M, Endoh K, Yoshikai T, Kudo S. Comparison between patient characteristics and cranial MR findings in chronic thinner intoxication. Eur Radiol 2002;12:1338-1341. 11) Thajeb P, Shih BF, Wu MC. Crossed cerebellar diaschisis in herpes simplex encephalitis. Eur J of Radiol 2001;38:55-58. 12) Pantano P, Baron JC, Samson Y, et al. Crossed cerebellar diaschisis: further studies. Brain 1986;109:677-694. 13) Chung HD. Retrograde crossed cerebellar atrophy. Brain 1985;108;811-889. 14) Rollins NK, Wen TS, Dominguez R. Crossed cerebellar atrophy in children: a neurologic sequela of extreme prematurity. Pediatr Radiol 1995;25:S20-25. 15) Savoia rdo M , Strada L, Gir otti F, Zimm erma n RA, G risoli M, T esta D, Petr i lo R .Olivo pontocer ebella r atr ophy:MR dia gnosis an d relationship to mu ltisystem a troph y. R adiology 1990;174:693-696. 16) Nakaga wa N , Katayama T , Makita Y, et al. A case of spinocerebella r ataxia type 6 mimicking olivo pontocerebellar at rophy. N eur oradiology 199 9;41:503 -505. 17) Lee J, Lacomis D , Comu S, et al. Acquired hepatocerebral degeneration: MR and pathologic findings. AJNR AM J Neuroradiol 199 8;19:485 -487. 18) Brun berg JA , Jacquemont S, Hag erma n RJ, et al. Fr agile X prem utation car riers: C haracter istic MR im aging findings of ad ult male patients with pr ogr essive cereb e lar and cognitive dysfun ction. AJNR Am J Neur or adiol 2 002;23:1757-1766 19) van der Knaap MS, Ba rth PG , G abre els F J, et a l. A ne w leukoencephalo pathy with vanish ing white matte r. Ne urology 19 97;48:845-855. 20) Ormerod IE, Miller DH, McDonald WI, du Boulay EP, Rudge P, Kendall BE, Moseley IF, Johnson G, Tofts PS, Halliday AM. The role of NMR imaging in the assessment of multiple sclerosis and isolated neurological lesions. A quantitative study. Brain 1987;110:1579-1616. 21) Whiteman ML, Post MJ, Berger JR, Tate LG, Bell MD, Limonte LP. Progressive multifocal leukoencephalopathy in 47 HIV-seropositive patients: neuroimaging with clinical and pathologic correlation. Radiology 1993;187:233-40. Conclusion Conclusion Lesions in the middle cerebellar peduncle include various pathological conditions, ranging from infarction, tumor, infection, trauma and demyelination to primary and secondary degeneration. Understanding the anatomy, pathology, imaging characteristics is important for the differential diagnosis of lesions in the middle cerebellar peduncle. A. Coronal FLAIR image. B,C,D, Sagittal T1WI. E, Axial T2WI. F. FLAIR image occasionally shows slightly high signal intensity in the normal superior (not shown), inferior and middle cerebellar peduncles. middle cerebellar peduncle (m), superior cerebellar peduncle (s), inferior cerebellar peduncle (i). brain stem portion (B), ventricular portion (V), and cerebellar portion (C) of the middle cerebellar peduncle. A B C D E F m m s s i i m m m i i i s B V C Introduction Introduction Lesions in the cerebellar peduncle include variou s pathological conditions: infarction, various primary or secondary degeneration, demyelinatiing disease, toxic metabolic diaease, trauma, and benign and malignant tumors. Their differential diagnoses are occasionally difficult. We illustrate the anatomy, pathology and imaging findings of the cerebellar peduncle. Anatomy Anatomy Gross anatom y (Figure 1A-F). The cerebellum is connected to the brainstem by three cerebellar peduncles: 1) the inferior cerebellar peduncle (restiform body and juxtrarestiform body) 2) the middle cerebellar peduncle (brachium pontis), and 3) the superior peduncle (brachium conjunctivum) (1). The wall and lateral roof of the 4th ventricle are formed by the inner surfaces of t he ce rebellar pedun cles; the rost ral port ion by the superior peduncles; and the caudal portions by the inferior peduncles (Figure 1A -F). The middle cerebellar peduncle is lateral to inferior and superior peduncles and is not directly exposed to the cavity of the 4th ventricle. The middle cerebellar peduncle can be divided into three portions: brain stem portion, ventricular portion, and cerebellar portion (Figure 1E). This classification can be a useful application in surgery (2). Cerebellar connections (Figure 1G). The cerebellum is linked to other parts of the brain by numerous efferent and afferent fibers that are grouped together on each side of the cerebellum in three peduncles (1). Most of the afferent tracts enter the cerebellum via the inferior and middle cerebellar peduncles. A few enter via the superior cerebellar peduncle. Afferent fibers are far more numerous that efferent fibers by a ratio of 40:1 (3). The cortico-ponto- cerebellar pathway, composed of the corticopontine tra ct and the pontocerebellar tract, i s major afferent fibers through the middle cerebellar peduncle. It arises from the cerebral cortex and enter the ipsilateral pontine nucleous and almost entirely crossed to the contralateral cerebellum. Olivocerebellar fibers form the large st component of the inferior cerebellar peduncle. Most of efferent tracts of the cerebellum are via the superior cerebellar peduncle. They mostly arise from dentate nucleus and decussate at the levels through the inferior collicu lus. Most of the fibers enter the contralateral red nucleus and project the cerebral cortex via the thalamus. Symptomatology Lesions of the cerebellar peduncle result in variable clinical symptoms, ranging from vertigo or vomiting as the only clinical presentation to facial palsy, ataxia, nystagmus, diplopia, dysphagia, dysarthria, deafness, contralateral motor weakness, trigeminal sensory loss, dysmetria of the limb, loss of pain and temperature sense, Horner's syndrome, and "locked-in" syndrome (1,4,5). Imaging of normal anatom y(Figure 1F). The posterior fossa is difficult to evaluate on CT because of poor contrast resolution and artifacts. MRI more clearly demonstrates the anatomy and pathology of the middle cerebellar peduncle in the posterior fossa than does CT. FLAIR images occasionally show a slight increase in signal intensity in normal middle cerebellar peduncles (Figure 1F). Figure 1. Normal anatomy. Crossed cerebellar diaschisis and atrophy (Figures 10 and 11) Crossed cerebellar diaschisis and atrophy presumed to be associated with transneuronal metabolic depression in the cerebellum through cortico- ponto-cerebellar pathways (middle cerebellar peduncle) or other pathways su ch as cerebello-rubro-thalamic tract (superior cerebellar peduncle) (Figure 10) (12,13) Unilateral atrophy of the middle cerebellar peduncle and cerebellar hemisphere occurs as a sequela of ischemic or destructive injury of the contralateral cerebral hemisphere (14). These findings are found in children with a history of extreme prematurity, perinatal intracranial hemorrhage, and recurrent seizures (Figure 11). Solvent encephalopathy Solvent encephalopathy (Figure 8) There have been a few case reports of middle cerebellar peduncle lesions in solvent encephalopathy (chronic toluene intoxication) in which the cerebral and cerebellar white matter, thalamus, basal ganglia, internal capsule, and brain stem are also involved (9, 10) (Figure 8). These patients' symptoms are usually composed of pyramidal tract and cerebellar signs. The middle cerebellar peduncle lesions can be primary or secondary degeneration. A. T2WI shows right cerebral atrophy with ventricular dilatation representing a sequela of perinatal intracranial hemorrhage. B. T2WI through the posterior fossa shows atrophy of the contralateral cerebellar middle cerebellar peduncle (arrow) and hemisphere. Wallerian degeneration of ipsilateral brain stem is also seen (arrow). Figure 11. Crossed cerebellar atrophy 19-year-old female. She had a history of recurrent seizures and perinatal intracranial hemorrhage. A B Herpes encephalitis (Figure 9) Bilateral middle cerebellar peduncle lesions were present in a patient with herpes encephalitis with bilateral temporal lobe involvement (Figure 9). The cause of these lesions is unknown. Secondary transneuronal degeneration via bilateral cortico-ponto-cerebellar pathways may be one of the possible explanations for these lesions (Figure 6G) (11). Figure 9. Herpes encephalitis 40-year-old male presenting with a seizure. A. T2WI shows diffuse hyperintense lesions in the cortex and white matter in bilateral temporal lobes, which represents herpes encephalitis. B. Coronal FLAIR image shows hyperintense lesions in the bilateral middle cerebellar peduncles (arrows) and the temporal lobes. A B A,B A mass lesion is located in the ventricular portion to the cerebellar portion of the left middle cerebellar peduncle. It is high signal on T2WI and low signal on T1WI and with no enhancement (not shown). This lesion can be removable by surgery. A,B Axial T2WI and sagittal T1WI shows an extra-axial cerebellopontine angle mass lesion which deviates the left middle cerebellar peduncle posteriorly and superiorly (arrows). Figure 18. Acoustic schwannoma. 17-year-old female presenting with hearing loss and progressive ataxia Figure 17. Low grade astrocytoma. 4-year-old boy presenting with autism. A B A B Figure 8. Solvent encephalopathy. 38- year-old man presenting with blurred vi sion , a taxi c speech and bilateral pyramidal signs. T2WI shows diffuse hyperintense lesions in the white matter of both temporal lobes and mildly hyperintense lesions in the pons and bilateral middle cerebellar peduncles (arrows). H. Guillain-Mollaret triangle and hypertrophic olivary degeneration The lesion involving the pontine nuclei can extend into the areas within the Guillain-Mollaret triangle, which causes hypertrophic olivary degeneration. A, B, T2WI and DWI show a hyperintense lesion, representing an acute infarct in the right middle cerebellar peduncle. A, B, FLAIR image and DWI show hyperintensity lesionsin the left cerebellar hemisphre, and the midbrain including the left superior cerebellar peduncle. A B A B Figure 2. An infarct in the inferior cerebellar peduncle. 72-year-old man with vertigo. Figure 4. infarcts involving the superior cerebellar peduncle. 58- year-old man with loss of consciousness. A. FLAIR image shows hyperintensity lesions in the right cerebellar hemisphere (arrows) and contralateral diffuse cerebral hyperintensity associated with status epilepticus. B,C. FLAIR images at the level of the brain stem show a hyperintense lesion in the right superior cerebellar peduncle (arrows). These findings suggest that crossed cerebellar diaschisis of this case is related to retrograde transneuronal degeneration through the cerebello-rubro-thalamic tract. Figure 10. Crossed cerebellar diaschisis 27-year-old male, presenting with status epilepticus. He has a history of recurrent generalized seizures. A B C Demyelinating Demyelinating disease: disease: multiple sclerosis (MS), acute multiple sclerosis (MS), acute disseminated encephalomyelitis (ADEM) and progressive disseminated encephalomyelitis (ADEM) and progressive multifocal multifocal leukoencephalopathy leukoencephalopathy (PML) (PML) (Figures 14-16) (Figures 14-16) Brain stem and cerebellar involvement including cerebellar peduncles is common in patients with MS and ADEM. Cerebellar symptoms and signs are commonly seen in 50-80% in MS patients. On MRI brainstem lesions in 68% and cerebellar lesions in 49%-88% were detected (20). These lesions in MS or ADEM are often bilateral but asymmetric (Figures 14 and 15). In PML involvement of the posterior fossa including the cerebellar peduncles is also common (32%). Isolated disease in the posterior fossa is in 10% of PML patients (21) (Figure 16). A, B.T2WI shows multiple asymmetric hyper-intense lesions in the pons, middle cerebellar peduncles (arrows) cerebellar hemispheres, and in the deep white matter, which is characteristic of MS. Figure 14. MS. 40-year-old woman with multiple sclerosis, presenting with speech disturbance and ataxia. A B Leukodystrophy Leukodystrophy and and leukoencephalopathy leukoencephalopathy (Figure 13). Some kinds of leukodystrophy and leukoencephalopathy can also involve in the cerebellar peduncles. This leukoencephalopathy with vanishing white matter is an autosomal recessive disorder with chronic and progressive episodes of rapid deterioration, provoked by fever and minor head trauma. This is primarily an axonopathy, with myelin being secondarily affected (19) (Figure 13). A. T2WI shows diffuse white matter signal abnormalities similar to CSF intensity. B. T2WI also shows hyperintense lesions in the central tegmental tracts (arrows), pyramidal tracts (arrows), and inferior and middle cerebellar peduncles with atrophy (arrows). Figure 13.Leukoencephalopathy with vanishing white matter. An 11 year-old boy. A B Olivopontocerebellar atrophy (OPCA) and other primary Olivopontocerebellar atrophy (OPCA) and other primary degenerative diseases degenerative diseases (Figure 12). OPCA is a degenerative disease characterized by atrophy of the pons, middle cerebellar peduncles, and cerebellar hemispheres. There are characteristic histologic changes, such as loss of specific fiber tracts and the presence of gliosis in the pons, middle cerebellar peduncles and cerebellum (15). The fibers affected in the pons are the transverse pontine fibers, while the pyramidal tracts and tegmentum are spared (Figure 12). Increased hyperintensity in the middle cerebellar peduncles are also report ed in other mu ltipl e system atrophy, autosomal do minan t spinocerebellar atrophy (16), Wilson’s disease, non-Wilsonian hepatocerebral degeneration (17), and fragile X syndrome (18). A, B. Axial and sagittal FLAIR images show hyperintensity in the middle (arrows) and inferior cerebral peduncles (arrows). C. Axial FLAIR image also shows cruciform hyperintensity in the transverse pontine fibers on the anterior and lateral aspect of the pons. The tegmentum (arrows ) and the pyramidal tracts (arrows) are spared. Figure 12. Ol ivopontocerebellar atrophy (sporadic type). 54-year- old woman presenting with dysarthric speech and dizziness. A B C A. T2WI shows an isolated hyperintense lesion in the right middle cerebellar peduncle extending into the cerebellar hemisphere. B. Gd-enhanced T1WI shows this lesion as hypointensity with no enhancement. Figure 16. PML. 25-year-old man presenting with right-sided weakness and headache. He has had a history of HIV infection. A B Figure 15. MS. 57-year-old man presenting with speech disturbance and ataxia. A B C D A, B.T2WI and FLAIR image shows hyperintense lesions in the pons, and inferior cerebellar peduncles (arrows), and in the callosomarginal interface in the deep white matter, which is characteristic of MS. C, D. Hyperintense lesions are also seen in the midbrain, and the superior cerebellar peduncle (arrows).
Transcript of Anatomy and Pathology of the Cerebellar Peduncle - asnr. · PDF fileof the upper brains tem...
Anatomy and Pathology of the Anatomy and Pathology of the CerebellarCerebellar Peduncle PeduncleToshio Moritani MD, PhD, Akio Hiwatashi MD, Henry Z Wang MD, PhD, Yuji Toshio Moritani MD, PhD, Akio Hiwatashi MD, Henry Z Wang MD, PhD, Yuji NumaguchiNumaguchi, MD, PhD, Leena Ketonen MD, PhD, Sven E Ekholm , MD, PhD, Leena Ketonen MD, PhD, Sven E Ekholm MD,PhDMD,PhD, Per-Lennart A Westesson MD, PhD, DDS, Per-Lennart A Westesson MD, PhD, DDS
Division of Diagnostic and Interventional Neuroradiology, Department of Radiology, University of Rochester Medical Center, Rochester NY Division of Diagnostic and Interventional Neuroradiology, Department of Radiology, University of Rochester Medical Center, Rochester NY FF E-mail: [email protected] E-mail: [email protected]
Infarction Infarction (Figures 2-5)
The inferior cerebellar peduncle is mainly supplied by the posteriorinferior cerebellar artery (PICA). The middle cerebellar peduncle issupplied by the anterior inferior cerebellar artery (AICA) and partly by thesuperior cerebellar artery (SCA). The superior cerebellar peduncle ismainly supplied by the SCA. These arteries vary greatly in origin, size,course, and supply area, the aera of infarction are variable in extent andlocation, ranging from a small infarct local ized into the cerebellarpeduncle (Figure 2 and 3) to large involvement of the cerebellarhemisphere, and can be associated with the involvement of pons,midbrain, thalamus and occipital lobe (Figure 4) (4). Bilateral AICAterritory infarcts are very rare (Figure 5), and can occur due tohypoperfusion in the watershed area between the AICA and the SCA (6).
Wallerian degeneration of the pontocerebellar tractsWallerian degeneration of the pontocerebellar tractssecondary to pontine hemorrhage or infarction secondary to pontine hemorrhage or infarction (Figure 6).
Wallerian degeneration secondary to pontine hemorrhage or infarction isusually bilateral. Differentiating from infarction is important. This is becauseof damage to both ipsilateral pontine nuclei (which deliver axons to thecontralateral cerebellar hemisphere) and the ipsilateral axons (whichoriginate from the contralateral pontine nuclei and course into the ipsilateralcerebellar hemisphere) (Figure 6G) (3). The T2 prolongations were firstrecognized from 26 days to 4.5 months after insult Theoretically, thewallerian degeneration of the pontocerebellar tracts should extend out tothe mossy fibers in the cerebellar cortex, as seen on the pathologicalspecimen; however this is beyond the resolution of MRI(3). Hypertrophicolivary degeneration occasionally coexists with these lesions, because thelesion can also involve the area in the Guillain-Mollaret triangle (Figure 6H)(7).
Figure 3. An infarct in the inferior cerebel lar peduncle. 57-year-old man with ataxia and diplopia.
A,B. T2WI and DWI at 24hrs after onset clearlyreveal homogenousround hyperintensityareas representing acuteinfarcts in the bilateralmiddle cerebellarpeduncles and bothcerebellar hemispheres.
A, B, FLAIR image andDWI show ahyperintense lesion,representing a smallacute infarct in the leftinferior cerebellarpeduncle.
Figure 5. Bilateral infarcts in the middle cerebellar peduncle. 80-year-old man with ataxia and vertigo.
A B
A B
G. Cerebellar connections. The cortico-ponto-cerebellar pathway(corticopontine tract and pontocerebellar tract) is major afferent fibersthrough the middle cerebellar peduncle. Olivocerebellar fibers (afferentfibers) are through the inferior cerebellar peduncle. Efferent fibersmainly arise from the dentate nucleus to the red nucleus through thesuperior cerebellar peduncle (cerebello-rubro-thalamic tract).
Osmotic Osmotic myelinolysismyelinolysis (Figure 7).
Symmetrical lesions in bilateral middle cerebellar peduncles without centralpontine myelinolysis (CPM) was reported as cerebellar peduncle myelinolysis(8). However, in our case, bilateral cerebellar peduncle lesions accompaniedby CPM (Figure 7). These lesions are presumed to be due to myelinolysisitself or secondary degeneration related to CPM.
Figure 6. Wallerian degeneraion in the middle cerebellarpeduncle. 50-year-old man with quadriparesis and loss ofconsciousness after chiropract ic.
F. On the pathologicalspecimen of anotherpatient, walleriandegeneration of thepontocerebellar tractsis recognized assymmetric roundedlesions (arrows) inbilateral middlecerebellar pedunclesand extends out to themossy fibers in thecerebellar cortex(open arrows)
(Ref. 3. Int J Neuroradiol1998;4:171-177.Toshihiro O'uchi MDwith permission).
A, B. DWI and T2WI shows hyperintense lesions in the right cerebellarhemisphere and the left side of the pons at 10 days after onset, whichrepresents subacute hemorrhagic infarcts.C, D. On follow-up MRI at 8 months after onset, old infarcts show very highintensity on T2WI and low intensity on FLAIR image as CSF. Symmetricalround hyperintense lesions in bilateral middle cerebellar peduncles are seenon T2WI and FLAIR image (arrows). These lesions represent walleriandegeneration of the pontocerebellar tracts secondary to pontine infarction.E. T2WI at the level of the medulla demonstrates symmetric hyperintenselesions corresponding to the bilateral olivary nuclei, representing hypertrophicolivary degeneration (arrows).
A B
F
G. Wallerian degenerationin bilateral middlecerebellar peduncles
The lesion involving thepontine nucleus can alsoinvolve the ponto-cerebellar tract from thecontralateral pontinenucleus, which results inwallerian degeneration inbilateral middle cerebellarpeduncles.
C D E
A. B. T2WI shows a hyperintense lesion in the central pons representing CPM.T2WI also shows symmetrical round lesions in the bilateral middle cerebellarpeduncles (arrows). These lesions maybe due to myelinolysis itself orsecondary degeneration.
Figure 7. CPM50-year-old femalepresenting with loss ofconsciousness afterrapid correction ofhyponatremia.
A B
Neurofibromatosis Neurofibromatosis (Figure 19)(Figure 19)
Hamarto matous lesions are observed in 80% of al l patients withneurofibromatosis type 1. Multiple lesions in the basal ganglia, opticradiation, brainstem, and cerebellar peduncles are common (Figure 19).Pathologically, these lesions are foci of hyperplastic or dysplastic glialproliferation and considered malformations rather than neoplasms.
Diffuse axonal injury (DAI) Diffuse axonal injury (DAI) (Figure 20)(Figure 20)
The gray-white matter interface, the corpus callosum, and dorsal aspectof the upper brainstem including the superior cerebellar peduncle arethree specific areas for the occurrence of DAI. Other less frequentlocations include the caudate nuclei, thalamus and internal capsule.Cerebellar involvement including the middle cerebellar peduncle isuncommon (Figure 20).
TumorTumor (Figures 17 and 18).
Benign tumors such as astrocytoma or cavernous angioma can involvein the cerebellar peduncle (Figures 17). An extra-axial tumor such asbenign acoustic schwannoma occasionally displaces the middlecerebellar peduncle (Figure 18). Malignant tumors such as metastasisor glioblastoma multiforme also o ccur in the cerebellar peduncle.Tumors involving the ventricular portion or the cerebellar portion of themiddle cerebellar peduncle can be removed by surgery (3).
A. FLAIR image shows ahyperintense lesion in the leftmiddle cerebellar peduncle tocerebellar hemisphere due toDAI.
B. DWI shows hyperintenselesions in the corpus callosumand bilateral internalcapsules, which is typicalfindings of DAI.
Figure 20. DAI. 29-year-old woman with DAI, presenting with loss ofconsciousness after motor vehicle accident.
A B
A,B T2WI and FLAIRimage showmultiple asymmetriclesions in the pons,middle and inferiorcerebellarpeduncles, andcerebellum.
Figure 19. Neurofibromatosis type 1. 4-year-old girl presentingwith developmental delay.
A B
Re feren ces
1) Carpenter MB. Cerebellum. In, Core Textbook of Neuroanatomy. 5th edition. Baltimore, MD: Williams &Wilkins, 1996;583-623.
2) Tomita T. Surgical management of cerebellar peduncle lesions in children. Neurosugery 1986;18:568-575.
3) O'uchi T. Wallerian degeneration of pontocerebellar tracts after pontine hemorrhage. Int J Neuroradiol 1998;4:171-177.
4) Amenco P, Rosengart A, DeWitt D, Pessin MS, Caplan LR. Anterior inferior cerebellar artery teritory infarcts. Mechanisms and clinicalfeatures. Arch Neurol 1993;50:154-161.
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ConclusionConclusionLesions in the middle cerebellar peduncle include various pathologicalconditions, ranging from infarction, tumor, infection, trauma anddemyelination to primary and secondary degeneration. Understandingthe anatomy, pathology, imaging characteristics is important for thedifferential diagnosis of lesions in the middle cerebellar peduncle.
A. Coronal FLAIR image. B,C,D, Sagittal T1WI. E, Axial T2WI.
F. FLAIR image occasionally shows slightly high signal intensity in thenormal superior (not shown), inferior and middle cerebellar peduncles.
middle cerebellar peduncle (m), superior cerebellar peduncle (s),inferior cerebellar peduncle (i).
brain stem portion (B), ventricular portion (V), and cerebellar portion (C)of the middle cerebellar peduncle.
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IntroductionIntroductionLesions in the cerebellar peduncle include variou s pathologicalconditions: infarction, various primary or secondary degeneration,demyelinatiing disease, toxic metabolic diaease, trauma, and benignand malignant tumors. Their differential diagnoses are occasionallydifficult. We illustrate the anatomy, pathology and imaging findings of thecerebellar peduncle.
AnatomyAnatomyGross anatomy (Figure 1A-F).
The cerebellum is connected to the brainstem by three cerebellarpeduncles: 1) the inferior cerebellar peduncle (restiform body andjuxtrarestiform body) 2) the middle cerebellar peduncle (brachiumpontis), and 3) the superior peduncle (brachium conjunctivum) (1). Thewall and lateral roof of the 4th ventricle are formed by the inner surfacesof the cerebellar pedun cles; the rost ral port ion by the superiorpeduncles; and the caudal portions by the inferior peduncles (Figure1A-F). The middle cerebellar peduncle is lateral to inferior and superiorpeduncles and is not directly exposed to the cavity of the 4th ventricle.The middle cerebellar peduncle can be divided into three portions: brainstem portion, ventricular portion, and cerebellar portion (Figure 1E).This classification can be a useful application in surgery (2).
Cerebellar connections (Figure 1G).
The cerebellum is linked to other parts of the brain by numerous efferentand afferent fibers that are grouped together on each side of thecerebellum in three peduncles (1). Most of the afferent tracts enter thecerebellum via the inferior and middle cerebellar peduncles. A few entervia the superior cerebellar peduncle. Afferent fibers are far morenumerous that efferent fibers by a ratio of 40:1 (3). The cortico-ponto-cerebellar pathway, composed of the corticopontine tra ct and thepontocerebellar tract, i s major afferent f ibers through the middlecerebellar peduncle. It arises from the cerebral cortex and enter theipsilateral pontine nucleous and almost entirely crossed to thecontralateral cerebellum. Olivocerebellar fibers form the large stcomponent of the inferior cerebellar peduncle. Most of efferent tracts ofthe cerebellum are via the superior cerebellar peduncle. They mostlyarise from dentate nucleus and decussate at the levels through theinferior collicu lus. Most of the fibers enter the contralateral red nucleusand project the cerebral cortex via the thalamus.
Symptomatology
Lesions of the cerebellar peduncle result in variable clinical symptoms,ranging from vertigo or vomiting as the only clinical presentation to facialpalsy, ataxia, nystagmus, diplopia, dysphagia, dysarthria, deafness,contralateral motor weakness, trigeminal sensory loss, dysmetria of thelimb, loss of pain and temperature sense, Horner's syndrome, and"locked-in" syndrome (1,4,5).
Imaging of normal anatomy(Figure 1F).
The posterior fossa is difficult to evaluate on CT because of poorcontrast resolution and artifacts. MRI more clearly demonstrates theanatomy and pathology of the middle cerebellar peduncle in theposterior fossa than does CT. FLAIR images occasionally show a slightincrease in signal intensity in normal middle cerebellar peduncles(Figure 1F).
Figure 1. Normal anatomy.
Crossed cerebellar diaschisis and atrophy (Figures 10 and 11)
Crossed cerebellar diaschisis and atrophy presumed to be associated withtransneuronal metabolic depression in the cerebellum through cortico-ponto-cerebellar pathways (middle cerebellar peduncle) or other pathwayssu ch as cerebello-rubro-thalamic tract (superior cerebellar peduncle)(Figure 10) (12,13) Unilateral atrophy of the middle cerebellar peduncleand cerebellar hemisphere occurs as a sequela of ischemic or destructiveinjury of the contralateral cerebral hemisphere (14). These findings arefound in chi ldren with a history of extreme prematurity, perinatalintracranial hemorrhage, and recurrent seizures (Figure 11).
Solvent encephalopathySolvent encephalopathy (Figure 8)
There have been a few case reports of middle cerebellar peduncle lesionsin solvent encephalopathy (chronic toluene intoxication) in which thecerebral and cerebellar white matter, thalamus, basal ganglia, internalcapsule, and brain stem are also involved (9, 10) (Figure 8). Thesepatients' symptoms are usually composed of pyramidal tract and cerebellarsigns. The middle cerebellar peduncle lesions can be primary orsecondary degeneration.
A. T2WI shows right cerebral atrophy with ventricular dilatation representinga sequela of perinatal intracranial hemorrhage.
B. T2WI through the posterior fossa shows atrophy of the contralateralcerebellar middle cerebellar peduncle (arrow) and hemisphere.Wallerian degeneration of ipsilateral brain stem is also seen (arrow).
Figure 11. Crossedcerebellar atrophy
19-year-old female.She had a history ofrecurrent seizures andperinatal intracranialhemorrhage.
A B
Herpes encephalitis (Figure 9)
Bilateral middle cerebellar peduncle lesions were present in a patient withherpes encephalitis with bilateral temporal lobe involvement (Figure 9).The cause of these lesions is unknown. Secondary transneuronaldegeneration via bilateral cortico-ponto-cerebellar pathways may be one ofthe possible explanations for these lesions (F igure 6G) (11).
Figure 9.Herpesencephalitis
40-year-old malepresenting witha seizure.
A. T2WI shows diffuse hyperintense lesions in the cortex and white matterin bilateral temporal lobes, which represents herpes encephalitis.
B. Coronal FLAIR image shows hyperintense lesions in the bilateral middlecerebellar peduncles (arrows) and the temporal lobes.
A B
A,B A mass lesion is locatedin the ventricular portion tothe cerebellar portion ofthe left middle cerebellarpeduncle. It is high signalon T2WI and low signalon T1WI and with noenhancement (notshown). This lesion canbe removable by surgery.
A,B Axial T2WI and sagittal T1WI shows an extra-axial cerebellopontineangle mass lesion which deviates the left middle cerebellar peduncleposteriorly and superiorly (arrows).
Figure 18.Acousticschwannoma.
17-year-old femalepresenting withhearing loss andprogressive ataxia
Figure 17. Low grade astrocytoma. 4-year-old boy presenting withautism.
A B
A B
Figure 8. Solvent encephalopathy. 38-year-old man presenting with blurredvi sion, ataxi c speech and bilateralpyramidal signs.T2WI shows diffuse hyperintense lesions inthe white matter of both temporal lobes andmildly hyperintense lesions in the pons andbilateral middle cerebellar peduncles (arrows).
H. Guillain-Mollarettriangle and hypertrophicolivary degenerationThe lesion involving thepontine nuclei can extendinto the areas within theGuillain-Mollaret triangle,which causes hypertrophicolivary degeneration.
A, B, T2WI and DWI show ahyperintense lesion,representing an acuteinfarct in the right middlecerebellar peduncle.
A, B, FLAIR image and DWIshow hyperintensitylesionsin the leftcerebellar hemisphre,and the midbrainincluding the left superiorcerebellar peduncle.
A B
A B
Figure 2. An infarct in the inferior cerebellar peduncle. 72-year-oldman with vertigo.
Figure 4. infarcts involving the superior cerebellar peduncle. 58-year-old man with loss of consciousness.
A. FLAIR image shows hyperintensity lesions in the right cerebellarhemisphere (arrows) and contralateral diffuse cerebral hyperintensityassoci ated with status epilepticus.
B,C. FLAIR images at the level of the brain stem show a hyperintenselesion in the right superior cerebellar peduncle (arrows). Thesefindings suggest that crossed cerebellar diaschi sis of this case isrelated to retrograde transneuronal degeneration through thecerebello-rubro-thalamic tract.
Figure 10. Crossed cerebellar diaschisis
27-year-old male, presenting with status epilepticus. He has a historyof recurrent generalized seizures.
A B C
DemyelinatingDemyelinating disease: disease: multiple sclerosis (MS), acutemultiple sclerosis (MS), acutedisseminated encephalomyelitis (ADEM) and progressive disseminated encephalomyelitis (ADEM) and progressive multifocalmultifocalleukoencephalopathyleukoencephalopathy (PML) (PML) (Figures 14-16)(Figures 14-16)
Brain stem and cerebellar involvement including cerebellar peduncles iscommon in patients with MS and ADEM. Cerebellar symptoms and signsare commonly seen in 50-80% in MS patients. On MRI brainstem lesionsin 68% and cerebellar lesions in 49%-88% were detected (20). Theselesions in MS or ADEM are often bilateral but asymmetric (Figures 14 and15). In PML involvement of the posterior fossa including the cerebellarpeduncles is also common (32%). Isolated disease in the posterior fossa isin 10% of PML patients (21) (Figure 16).
A, B.T2WI shows multipleasymmetric hyper-intenselesions in the pons, middlecerebellar peduncles(arrows) cerebellarhemispheres, and in thedeep white matter, which ischaracteristicof MS.
Figure 14. MS. 40-year-old woman with multiple sclerosis, presentingwith speech disturbance and ataxia.
A B
LeukodystrophyLeukodystrophy and and leukoencephalopathyleukoencephalopathy (Figure 13).
Some kinds of leukodystrophy and leukoencephalopathy can also involve inthe cerebellar peduncles. This leukoencephalopathy with vanishing whitematter is an autosomal recessive disorder with chronic and progressiveepisodes of rapid deterioration, provoked by fever and minor head trauma.This is primarily an axonopathy, with myelin being secondarily affected (19)(Figure 13).
A. T2WI shows diffuse whitematter signal abnormalitiessimilar to CSF intensity.
B. T2WI also showshyperintense lesions in thecentral tegmental tracts(arrows), pyramidal tracts(arrows), and inferior andmiddle cerebellar peduncleswith atrophy (arrows).
Figure 13.Leukoencephalopathy with vanishing white matter.
An 11 year-old boy.
A B
Olivopontocerebellar atrophy (OPCA) and other primaryOlivopontocerebellar atrophy (OPCA) and other primarydegenerative diseases degenerative diseases (Figure 12).
OPCA is a degenerative disease characterized by atrophy of the pons,middle cerebellar peduncles, and cerebellar hemispheres. There arecharacteristic histologic changes, such as loss of specific fiber tracts andthe presence of gliosis in the pons, middle cerebellar peduncles andcerebellum (15). The fibers affected in the pons are the transverse pontinefibers, while the pyramidal tracts and tegmentum are spared (Figure 12).Increased hyperintensity in the middle cerebellar peduncles are alsoreported in other multiple system atrophy, autosomal do minantspinocerebellar atrophy (16), Wilson’s disease, non-Wilsonianhepatocerebral degeneration (17), and fragile X syndrome (18).
A, B. Axial and sagittal FLAIR images show hyperintensity in the middle(arrows) and inferior cerebral peduncles (arrows).
C. Axial FLAIR image also shows cruciform hyperintensity in the transversepontine fibers on the anterior and lateral aspect of the pons. Thetegmentum (arrows ) and the pyramidal tracts (arrows) are spared.
Figure 12. Ol ivopontocerebellar atrophy (sporadic type). 54-year-old woman presenting with dysarthric speech and dizziness.
A B C
A. T2WI shows an isolatedhyperintense lesion inthe right middlecerebellar peduncleextending into thecerebellar hemisphere.
B. Gd-enhanced T1WIshows this lesion ashypointensity with noenhancement.
Figure 16. PML. 25-year-old man presenting with right-sidedweakness and headache. He has had a history of HIV infection.
A B
Figure 15. MS. 57-year-old man presenting with speech disturbanceand ataxia.
A B
C D
A, B.T2WI and FLAIRimage showshyperintense lesions inthe pons, and inferiorcerebellar peduncles(arrows), and in thecallosomarginalinterface in the deepwhite matter, which ischaracteristic of MS.
C, D. Hyperintenselesions are also seenin the midbrain, andthe superior cerebellarpeduncle (arrows).
