PROF DR. ÇİĞDEM ÖZKARA

BRAIN STEM ANATOMY & CLINICAL PRESENTATIONS

• In vertebrate anatomy the brainstem (or brain stem) is the posterior part of the brain, adjoining and structurally continuous with the spinal cord.

• The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves.

• Though small, this is an extremely important part of the brain as the nerve connections of the motor and sensory systems from the main part of the brain to the rest of the body pass through the brain stem.

• This includes the corticospinal tract (motor), the posterior column-medial lemniscus pathway (fine touch, vibration sensation and proprioception) and the spinothalamic tract (pain, temperature, itch and crude touch).

• The brain stem also plays an important role in the regulation of cardiac and respiratory function. It also regulates the central nervous system, and is pivotal in maintaining consciousness and regulating the sleep cycle.

BRAIN STEM

Includes:medulla oblongata (myelencephalon), pons (part of metencephalon), midbrain (mesencephalon).Less frequently, parts of the diencephalon are

included.

1.Cerebrum2.Thalamus3.Mesencephalon - Midbrain4.Pons5.Medulla oblongata6.Medulla spinalis - Spinal cord

The midbrain is divided into three parts. The first is the tectum, which is "roof" in Latin. The tectum includes the superior and inferior

colliculi and is the dorsal covering of the cerebral aqueduct. The inferior colliculus, involved in the sense of hearing sends its inferior brachium to the medial geniculate body of the diencephalon.

Superior to the inferior colliculus, the superior colliculus marks the rostral midbrain. It is involved in the special sense of vision and sends its superior brachium to the lateral geniculate body of the diencephalon.

The second part is the tegmentum and is ventral to the cerebral aqueduct.

Several nuclei, tracts and the reticular formation are contained here.

Last, the ventral side is composed of paired cerebral peduncles. These transmit axons of upper motor neurons.

Midbrain (mesencephalon)

MidbrainPeriaqueductal gray: The area around the cerebral aqueduct, which

contains various neurons involved in the pain desensitization pathway. Neurons synapse here and, when stimulated, cause activation of neurons in the nucleus raphe magnus, which then project down into the dorsal horn of the spinal cord and prevent pain sensation transmission.Occulomotor nerve nucleus: This is the nucleus of CN III.Trochlear nerve nucleus: This is the nucleus of CN IV.Red Nucleus: This is a motor nucleus that sends a descending tract to the lower motor neurons.Substantia nigra: This is a concentration of neurons in the ventral portion of the midbrain that uses dopamine as its neurotransmitter and is involved in both motor function and emotion. Its dysfunction is implicated in Parkinson's Disease.Reticular formation: This is a large area in the midbrain that is involved in various important functions of the midbrain. It contains lower motor neurons, is involved in the pain desensitization pathway, is involved in the arousal and consciousness systems, and contains the locus ceruleus, which is involved in intensive alertness modulation and in autonomic reflexes.Central tegmental tract: Directly anterior to the floor of the 4th ventricle, this is a pathway by which many tracts project up to the cortex and down to the spinal cord.

BEYİN SAPI

• Mezensefalon beyinsapının en üst bölümünü oluşturur. Üçüncü (N. Oculomotorius) ve IV. (N. Trochlearis) kranyal sinirlerin nukleusları buradadır

Fibria Corticospinalis

Substania Nigra

N.oculomotorius(CN3): has 2 nuclei:Nüc nervi oculomotorii motor nucleus. At

collikulus superior : All extraoculer mucles except for M.obliquus superior & m.rectus lateralis & m.levator palpebra superioris i were innervated . Upward and internal gaze

nüc visseralis (edinger westphal): Parasympathetic nucleus. Innervates M. sphincter pupillae & M. ciliaris.

Lesion: ptosis , mydriazis, eye down and out deviation, vertical diplopi , light reflex & accomodation loss.

N.Oculomotorius III

• Only somatomotor . • M.obliquus superioru

innervation.• Unique CN leaves brain stem

from posterior• Lesion: cannot look down

and out , vertikal diplopi Complains when coming down the stairs.

• If nucleus n. troclearisin is damaged: contrlateral m.obliquus superior is effected (exception for other CN)

N. trochlearis(CN4)

• Weber sendromu: (superior alternating hemiplegia) is a form of stroke characterized by the presence of an oculomotor nerve palsy and contralateral hemiparesis or hemiplegia. It is caused by midbrain infarction as a result of occlusion of the paramedian branches of the posterior cerebral artery or of basilar bifurcation perforating arteries.[1]

1. Substantia nigra, akinesia (parkinsonism)2. Corticospinal fibers, contralateral spastic hemiplegia3. Corticonuclear fibers, contralateral lower facial and hypoglossal paralysis, supranuclear4. Corticopontine tract, contralateral dystaxia5. Root fibers of oculomotor nerve, ipsilateral oculomotor paralysis with wide fixed pupil

1. Medial lemniscus, contralateral decrease in sensations of touch, position, and vibration2. Red nucleus, contralateral hyperkinesia (chorea, athetosis)3. Substantia nigra, contralateral akinesia (parkinsonism)4. Root fibers of oculomotor nerve, ipsilateral oculomotor paralysis, wide fixed pupil

BENEDIKT SYNDROME: Caused by a lesion ( infarction, hemorrhage, tumor, or tuberculosis) in the tegmentum of the midbrain and cerebellum. It can result from occlusion of the posterior cerebral arteryCharacterized by the presence of an CN III oculomotor nerve palsy and contralateral hemiparesis (weakness) and cerebellar ataxia including tremor. Neuroanatomical structures affected include CNIII nucleus, Red nucleus, corticospinal tracts, brachium conjunctivum, and cerebellum.

Parinaud's Syndrome : results from injury, either direct or compressive, to the dorsal midbrain. Specifically, compression or ischemic damage of the mesencephalic tectum, including the superior colliculus adjacent oculomotor (origin of cranial nerve III) and Edinger-Westphal nuclei, causing dysfunction to the motor function of the eye.

1. Cerebral aqueduct, stenosis with occlusive hydrocephalus2. Superior colliculi, conjugated upwards gaze paralysis3. Oculomotor nucleus, eventual oculomotor paralysis and ptosis (trochlear paralysis)4. Medial longitudinal fasciculus, nystagmus

A. Pinealoma compressing superior colliculi and aqueduct.B. Nuclei of III (IV) and medial longitudinal tracts are within range of deformation.

PONSNamed after the Latin word for "bridge" or the 16th-

century], It is superior to (up from) the medulla oblongata, inferior to (down from) the midbrain, and ventral to (in front of) the cerebellum.

In humans and other bipeds this means it is above the medulla, below the midbrain, and anterior to the cerebellum. This white matter includes tracts that conduct signals from the cerebrum down to the cerebellum and medulla, and tracts that carry the sensory signals up into the thalamus.

Posteriorly, it consists mainly of two pairs of thick stalks called cerebellar peduncles. They connect the cerebellum to the pons and midbrain.

The pons contains nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.[3]

Within the pons is the pneumotaxic center, a nucleus in the pons that regulates the change from inspiration to expiration.[

• Cranial nerves are the abducens nerve VI, facial nerve VII and the vestibulocochlear nerve VIII, respectively.

• At the level of the midpons, trigeminal nerve V, emerges.

• N. trigeminus(CN5): has 3 sensoriel, 1 motor nucleus– nuc. spinalis nervi trigemini: related to cornea reflex– Nuc. spinalis nervi trigemini: face and head pain and

temperature sensations 2nd neuron.– Nuc. mesensefalikus nervi trigemini– Nuc. motorius nervi trigemini– Ganglion trigeminale (gasser ganglionu semilunar

ganglion): sensation ganglion

N. Trigeminus branches

• N.ophtalmikus (V1): only sensitive fibres. Bulbus oculi innervates, tip of nose, upper part of eyes .

• N.maksillaris(V2): only sensitive fibres , lower part

of eyes, upper lip innervation.• N.mandibularis(V3) Motor & sensitive fibres.

Masticatory muscles, lower lip and lower part of mouth , 2/3 anteror part of tongue , external ear and temporal region innervation.

• N.abducens(CN6): Only motor fibres. M.rektus lateralisi innervation. Lesion: effected eye pulled medially, horizontal diplopia. Lies in sinus kavernosus lateral to A. carotis interna

• Involves motor, sensory and parasympatic fibres:nüc.nervi facialis: Motor nuc.Innervates mimic

muscles :m.stapedius,m.stylohyoideus,m.digastrikus venter posteriorun

Nüc.lacrimalis ve nüc.salivatorius: Parasympathic nucleiNüc traktus soliterius:2.neurons of tasteCentral facial paralysis: Supranuclear lesions, mouth

commissure deviates to healthy side (lesion), can close eyes cornea reflex is normal.

Peripheric facial paralysis (Bell’s palsy): Intranuclear or infranuclear mouth commissure deviates to healthy side , cornea reflex disappears, cannot close eye

N.facialis(CN7)

Millard-Gubler syndromeIt is a syndrome of unilateralsoftening of the brain tissuearising from obstruction of theblood vessels of the pons.VI and VII cranial nerves fibers of the corticospinal tract,Clinical presentation: Paralysis of the abducens (including

diplopia, internal strabismus, and loss of power to rotate the affected eye outward)

facial nerves ( peripheric ipsilateral)

Contralateral Hemiplegia of the extremities. It is also known as

"crossed hemiplegia".

1. Medial lemniscus, contralateral decrease of touch, position and vibration sensations in the lower extremities2. Lateral lemniscus, hypacusia3. Nucleus of facial nerve, peripheral ipsilateral paralysis of facial muscles4. Anterior spinothalamic tract, contralateral analgesia and thermanesthesia of body5. Pyramidal tract, contralateral spastic hemiplegia6. Abducent nerve, ipsilateral peripheral paralysis of lateral rectus muscle

Peripheral facial paralysis

Central facial paralysis

• N.vestibulocohlearis: N.vestibularis: carries the informaion related to position and movements of of head , N.cohlearis: primery audituar fibres.

Kranyal Sinirler (devam)

Medulla oblongata (bulbus) is the lower half of the brainstem. The medulla contains the cardiac, respiratory, vomiting and vasomotor centers and deals with autonomic functions, such as breathing, heart rate and blood pressure.

Functions

• The medulla oblongata controls autonomic functions, and relays nerve signals between the brain and spinal cord.

• It is also responsible for controlling several major points and autonomic functions of the body:

• respiration– chemoreceptors• cardiac center – sympathetic, parasympathetic system• vasomotor center – baroreceptors• reflex centers of vomiting, coughing, sneezing, and

swallowing• balancing the human body.

Nuclei of Medulla oblongata

Last five cranial nerve nuclei: • Nuc. Grasilis ve nuc. kuneatus: second neurons of conscious

proprioceptive, vibration, two point discrimination sensations• Nuc. Traktus solitarius: Related to VII,IX,X. cranial nerves.

Upper part is called nuc. Gustatorius and involves neurons of taste

• Nuc. Spinalis nervi trigemini: Pain and temparature sensation of face

• Nuc. Ambiguus: motor nuclei of IX,X,XI cranial nerves• Nuc. Salivatorius inferior: Parasempatik nuclei of XI. CN .

The fibres from this nuclei goes to glandula parotidea

N. Glossofaryngeus(CN93 nuclei, 2 ganglions,

Motor: nüc.ambiguus…. İnnervates m.stylofaringeus

Nüc salivatorius inferior parasempatik nucleus, innervates glandula parotidea

Nuc traktus solitarius 1/3 posterior of taste sensation of tongue , tonsilla palatina and middle ear sense.

Lesion: uvula deviates to healthy side .The integrity of the glossopharyngeal nerve

may be evaluated by testing the patient's general sensation and that of taste on the posterior third of the tongue. The gag reflex can also be used to evaluate the glossphyaryngeal nerve

N.vagus(CNX) 3 nuclei, 2 ganglion Motor nuc: nuc.ambiguus,Parasympatic nuc: nuc posterior nervi vagi, Taste : nuc. ractus solitarius The vagus nerve supplies motor parasympathetic

fibers to all the organs except the suprarenal (adrenal) glands, from the neck down to the second segment of the transverse colon. The vagus also controls a few skeletal muscles, namely:

• Cricothyroid muscle• Levator veli palatini muscle• Salpingopharyngeus muscle• Palatoglossus muscle• Palatopharyngeus muscle• Superior, middle and inferior

pharyngeal constrictors• Muscles of the larynx (speech).

• This means that the vagus nerve is responsible for such varied tasks as heart rate, gastrointestinal peristalsis, sweating, and quite a few muscle movements in the mouth, including speech (via the recurrent laryngeal nerve) and keeping the larynx open for breathing (via action of the posterior cricoarytenoid muscle, the only abductor of the vocal folds). It also has some afferent fibers that innervate the inner (canal) portion of the outer ear, via the Auricular branch (also known as Alderman's nerve) and part of the meninges. This explains why a person may cough when tickled on their ear (such as when trying to remove ear wax with a cotton swab)

N.accessorius(CNXI)

• Pure motor. • Some fibres from bulbus some

from servikal m. Spinalis sup. Segment ant horn cells.

• Leaves cranial cavity from foramen jugulare very close to IX. & X. CNs

• The nerve functions to control the sternocleidomastoid and trapezius muscles.

N. Hypoglossus (CNXII)

Motor nerve of tongue. Nucleus in bulbus. Lesion: tongue deviates

to the paralysed side, atrophy at that side

Unilateral involment: No tongue movements

IŞIK REFLEXİ

1. Inferior vestibular nucleus, nystagmus and ipsilateral inclination to fall2. Dorsal nucleus of vagus nerve, tachycardia and dyspnea3. Inferior cerebellar peduncle, ataxia and ipsilateral asynergia4. Nucleus of solitary tract, ageusia ipsilateral5. Ambiguus nucleus, ipsilateral paralysis of palate, larynx, and pharynx6. Nucleus of cochlear nerve, hypacusia7. Nucleus of trigeminal spinal tract, ipsilateral analgesia and thermanesthesia of face8. Central sympathetic pathway, Horner's syndrome. Hypohidrosis, ipsilateral vasodilation in face9. Anterior spinocerebellar tract, ataxia, ipsilateral hypotonia10. Lateral spinothalamic tract, analgesia and thermanesthesia contralateral over body

WALLENBERG’S SYNDROME (lateral medulla syndrome) It is the clinical manifestation resulting from occlusion of the posterior inferior cerebellar artery (PICA) or one of its branches or of the vertebral artery, in which the lateral part of the medulla oblongata infarcts, resulting in a typical pattern.

• Miyozis• Pitozis• Anhidrozis

Horner sendromu

• Medial medüller syndrome(Dejerine’in anterior medüller sendrom: Obstruction of a. spinalis anterior veya a. vertebralis

1. Medial longitudinal fasciculus, nystagmus2. Medial lemniscus, contralateral decrease of touch, vibration, and position sensations3. Olive, ipsilateral myorhythmia in velum and pharynx4. Hypoglossal nerve, ipsilateral flaccid paralysis of hypoglossal muscle with atrophy5. Pyramidal tract, contralateral, spastic hemiplegia with positive Babinski reflex

Tractus Pyramidalis

Spinothalamic tract: pain, tempartature, itch, crude touch

Posterior column fine touch, vibration, conscious proprioceptive

Cortico spinal tract: motor

Cranial nerve reflexes

Kranyal Sinirler (devam)