Clinical aspects of the nervous system
Transcript of Clinical aspects of the nervous system
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Clinical Neuroanatomy
Prof. Vajira Weerasinghe
Professor in Neurophysiology, Faculty of Medicine, University of Peradeniya
& Consultant Neurophysiologist, Teaching Hospital, Peradeniya
www.slideshare.net/vajira54
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Why study nervous system?
• Neurological diseases are very disabling and very little treatment is available
• Understanding the structure and function of the nervous system helps to understand the pathophysiological basis of these diseases
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Functional Subdivisions
• Sensory functions feeling, eg. pain
• Motor functionsmovement, eg. walking
• Integrative functionseg. reflexes
• Autonomic functionscontrol of blood pressure
• Higher functionsmemory, learning
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Anatomical Subdivisions• Central Nervous system
Brain and spinal cord
• Peripheral Nervous systemCranial Nerves & Peripheral Nerves
• Autonomic systemsympathetic & parasympathetic
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Disorders of the nervous system based on an anatomical divisions
Type of disorder example 1. Peripheral neuropathies
1. Polyneuropathies diabetic polyneuropathy 2. Mononeuropathies carpal tunnel syndrome
2. Neuromuscular junction disorders1. Presysnaptic disorders botulism 2. Postsynaptic disorders myasthenia gravis
3. Anterior horn cell diseases MND (motor neuron disease) 4. Plexus, spinal root or spinal cord disorders Erb’s palsy, cervical
spondylosis, intervertebral disc prolapse
5. Brainstem disorders Tumors 6. Strokes CVA 7. Basal ganglia disorders Parkinsonism 8. Cerebellar disorders Cerbellar ataxia 9. Memory and cognitive function disorders Alzheimer Disease 10. Cranial nerve lesions Bell’s palsy 11. Others Multiple sclerosis
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Peripheral neuropathies • Peripheral nerves are affected
• Types: Polyneuropathies or mononeuropathies
• Components: Sensory, motor, autonomic or mixed
• Distribution: Symmetrical or asymmetrical
• Cause: Trauma, demyelination, degeneration
• Examples: Diabetes mellitus vitamin deficiency alcoholism carpal tunnel syndrome ulnar nerve lesions wrist drop foot drop tarsal tunnel syndrome
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NMJ disorders• Myasthenia gravis
Antibodies to Ach receptors Post synaptic disorder
• Lambert Eaton Syndrome (myasthenic syndrome) Presynaptic disorder (antibodies against Ca channels)
• Botulism Presynaptic disorder Binds to the presynatic region and prevent release of Ach
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NMJ disorders
• Snake venom (Presynaptic or postsynaptic disorder)Krait (bungarotoxin)
Postsynaptic disorder
CobraPostsynaptic disorder
Russell’s viperPresynaptic disorder
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Snake venom
• Common Krait (bungarus caeruleus)Produces neurotoxin known as
bungarotoxin Very potent
Causes muscle paralysis and death if not treated
• Cobra venom contain neurotoxin
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Myasthenia gravis• Serious neuromuscular disease
• Antibodies form against acetylcholine nicotinic postsynaptic receptors at the NMJ
• Characteristic pattern of progressively reduced muscle strength with repeated use of the muscle and recovery of muscle strength following a period of rest
• Present with ptosis, fatiguability, speech difficulty, respiratory difficulty
• Treated with cholinesterase inhibitors
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Anterior cell diseases
• Relatively rare
• Affect any age
• Muscle wasting
• Example: Poliomyelitis
• Adults: MND (motor neuron disease), also called ALS (amyotrophic lateral sclerosis) Speech difficulty (dysarthria)Typical features in EMG test
• Infants: SMA (spinal muscular atrophy) Breathing difficulty
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MND dysarthria video clip
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Plexus, spinal root or spinal cord disorders
• Plexopathies: brachial plexus, lumbosacral plexus Erb’s palsy
• Radiculopathies: cervical, thoracic, lumbar, sacral roots
• Myelopathies: cervical, thoracic
• Cauda equina lesions
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Brainstem disorders • Sensory motor dysfunction and other features associated with brainstem
• Cranial nerve nuclei could be affected
• Tumors or trauma
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Motor homunculus
First discoveredbyPenfield
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Brodmann areas Primary motor cortex Area 4
Primary somatosensory Cortex, Area 3b, 1
Primary visual cortexBroca’s area area 44
Supplementary motor areaPremotor cortex
Secondary sensory area
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Motor cortex
• different areas of the body are represented in different cortical areas in the motor cortex
• Motor homunculus– somatotopic representation – not proportionate to structures but proportionate
to function – distorted map– upside down map
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Motor cortical areas
• primary motor cortex (MI)– precentral gyrus
• secondary motor cortex (MII)– premotor cortex– supplementary motor area (SMA)
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Stroke • Also called CVA (cerebrovascular accident) or brain attack
• 2nd most common cause of death worldwide (WHO)
• 4th most common cause of death in Sri Lanka
• Commonly hemiplegia occurs
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Types of strokes
• Ischaemic strokes (acute ischemic stroke is caused by thrombotic or embolic occlusion
of a cerebral artery and is more common than hemorrhagic stroke)
Large vessel strokes Lacunar strokes
• Haemorrhagic strokes (In hemorrhagic stroke, bleeding occurs directly into the brain
parenchyma due to a leakage from small intracerebral arteries damaged by chronic hypertension)
Intracerebral haemorrhage (ICH)Subarachnoid haemorrhage (SAH)
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CT images
Ischaemic strokes Haemorrhagic strokes
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Lacunar Stroke
• Lacunar infarcts or small subcortical infarcts result from occlusion of a single penetrating artery and account for one quarter of cerebral infarctions
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Cerebral blood vessels • Anterior and middle cerebral arteries carry the anterior circulation and arise
from the supraclinoid internal carotid arteries
• Anterior cerebral artery (ACA) supplies the medial portion of the frontal and parietal lobes and anterior portions of basal ganglia and anterior internal capsule
• Middle cerebral artery (MCA) supplies the lateral portions of the frontal and parietal lobes, as well as the anterior and lateral portions of the temporal lobes, and gives rise to perforating branches to the globus pallidus, putamen, and internal capsule
• MCA is the dominant source of vascular supply to the hemispheres
• Posterior cerebral arteries (PCA) arise from the basilar artery and carry the posterior circulation
• PCA gives rise to perforating branches that supply the thalami and brainstem and the cortical branches to the posterior and medial temporal lobes and occipital lobes
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Cerebellar arteries
• Inferiorly by the posterior inferior cerebellar artery (PICA), arising from the vertebral artery
• Superiorly by the superior cerebellar artery
• Anterolaterally by the anterior inferior cerebellar artery (AICA), from the basilar artery
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Lacunar infarct• Pure motor stroke/hemiparesis
This is the most common (33-50%) lacunar syndrome usually occurs with infarction of the posterior limb of the internal capsule, which carries the descending corticospinal and corticobulbar tracts, or the basis pontis. It is marked by hemiparesis or hemiplegia that typically affects the face, arm, or leg of one side. Dysarthria, dysphagia, and transient sensory symptoms may also be present.
• Ataxic hemiparesis This is the second most frequent lacunar syndrome and usually occurs with infarction of the posterior limb of the internal
capsule, basis pontis, and corona radiata. It displays a combination of cerebellar and motor symptoms, including weakness and clumsiness, on the ipsilateral side of the body. It usually affects the leg more than it does the arm; hence, it is known also as homolateral ataxia and crural paresis. The onset of symptoms is often over hours or days.
• Dysarthria/clumsy hand This is sometimes considered a variant of ataxic hemiparesis (above), but usually still is classified as a separate lacunar
syndrome. The lesion is in the pons and the main symptoms are dysarthria and clumsiness (i.e. weakness) of the hand, which often are most prominent when the patient is writing.
• Pure sensory stroke Marked by persistent or transient numbness, tingling, pain, burning, or another unpleasant sensation on one side of the
body, this infarct is usually in the contralateral thalamus.
• Mixed sensorimotor stroke This lacunar syndrome involves hemiparesis or hemiplegia with ipsilateral sensory impairment, with infarct typically in the
thalamus and adjacent posterior internal capsule.
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Watershed
• A watershed stroke or watershed infarct is defined as an ischemia, or blood flow blockage, that is localized to the border zones between the territories of two major arteries in the brain
• Watershed locations are those border-zone regions in the brain supplied by the major cerebral arteries where blood supply is decreased
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Basal Ganglia disorders
• Parkinsonism
• Athetosis
• Chorea
• Hemiballismus
Basal ganglia disorders are also called extrapyramidal disorders
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Basal ganglia• Caudate nucleus • Putamen• Globus pallidus
–(internal and external)• Subthalamic nuclei• Substantia nigra
International Basal Ganglia Society
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(Ref. Guyton)
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thalamus
globus pallidus
putamencaudate
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Basal ganglia• caudate nucleus
• putamen
• globus pallidus
• subthalamic nuclei
• substantia nigra
corpus striatum
lentiformnucleus
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Parkinsonism• due to destruction of dopamine secreting pathways from
substantia nigra to caudate and putamen. also called “paralysis agitans” or “shaking palsy” first described by Dr. James Parkinson in 1817.
• In the west, it affects 1% of individuals after 60 yrs
Classical Clinical features:
• Tremor, resting
• Rigidity of all the muscles
• Akinesia (bradykinesia): very slow movements
• Postural instability
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Chorea• Lesions in the caudate
nucleus
• jerky movements of the hand, face and other parts
• patient is unable to control them
• may get worse with anxiety
• disappears in sleep
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Athetosis
• Lesions in putamen
• spontaneous slow writhing movements (twisting movements) of fingers, hands, toes, feet.
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Hemiballismus
• Lesions in subthalamus
• violent, flailing movements of arm & leg on one side of the body
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Features of cerebellar disorders
• ataxia incoordination of movementsataxic gait
broad based gaitleaning towards side of the lesion
• dysmetriacannot plan movements
• past pointing & overshoot
• decomposition of movements
• intentional tremor
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Features of cerebellar disorders
• dysdiadochokinesisunable to perform rapidly alternating movements
• dysarthriaslurring of speech
• nystagmusoscillatory movements of the eye
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Features of cerebellar disorders
• hypotonia reduction in tone
due to excitatory influence on gamma motor neurons by cerebellum (through vestibulospinal tracts)
• decreased reflexes
• head tremor
• head tilt
• ReboundIncreased range of movement with lack of normal recoil to
original position
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Memory and cognitive function disorders
• Amnesia Retrograde amnesia
unable to recall events that occurred before the development of the amnesia for example due to head injury
Antegrade amnesiadifficulty in the learning and retention of information encountered after brain
damage, previous memories unaffectedCould occur in head injury, hippocampal lesions, alcoholism,
A combination of both
• Dementia Alzheimer’s disease
Loss of Ach pathways Alcoholism
Degeneration of nerve pathways Senile dementia
Old age
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limbic system
• nuclei– amygdala– septal nuclei– mammillary body– hypothalamus
• cortical areas– hippocampal gyrus– cingulate gyrus– dentate gyrus– entorhinal, amygdaloid cortex
• paralimbic structures• orbital gyrus, insula, nucelus accumbens, thalamic nuclei, superior
temporal gyrus,
• fibre tracts: fornix, medial forebrain bundle
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limbic cortex
• consist of 3 layered cortex (in contrast to 6 layered cortex of the neocortex)
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Dementia
• Loss of memoryAlzheimer’s dementia
degeneration of brain areas (hippocampus)decreased acetylcholine
Alcoholism limbic system (hippocampus) is affected
In old agesenile dementia
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Alzheimer’s disease
video
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Alzheimer’s disease
• A progressive, degenerative and fatal brain disease
• in which cell to cell connections in the brain are lost
• as a result, the death of brain cells occur
• Rapid cognitive impairment
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Other conditions
• Internuclear ophthalmoplegiaEye movement disorder Affected eye weak adduction, other eye nystagmusMedial longitudinal fasciculus (MLF) which connects
abducens and occulomotor pathways affected
Horner’s syndromeresults from an interruption of the sympathetic nerve supply to the eye and is characterized by the classic triad of miosis (ie, constricted pupil), partial ptosis, and loss of hemifacial sweating (ie, anhidrosis).
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Klippel–Feil syndrome
• This is a rare disease, initially reported in 1912 by Maurice Klippel and André Feil from France characterized by the congenital fusion of any 2 of the 7 cervical vertebrae