Brainstem

Question 1

cerebral aquaduct

Answer 1

common site of obstruction that results in noncommunicating hydrocephalus

periaqueductal gray contains neurons with opiod receptors that are stimulated by the spinomesencephalic component of the anterolateral system; these neurons function in the suppression of pain.

Question 2

Lesion of corticospinal tract axons

Answer 2

in the brainstem above the decussation may result in spastic hemiparesis in the limbs contralateral and below the lesion

Question 3

Complete lesion of the medial lemniscus

Answer 3

in the brainstem may result in a loss of touch, vibration, and pressure sensations in the upper and lower limb, neck, and trunk contralateral and below the lesion

Question 4

Lesion of the spinothalamic tract

Answer 4

in the brainstem may result in a loss of pain and temperature sensations from the upper and lower limb, neck, and trunk contralateral and below the lesion

Question 5

Horner’s Syndrome

Answer 5

patients with a lesion of the descending hypothalamic axons in the brainstem may have a central Horner’s Syndrome that is always ipsilateral to the side of the lesion. Patients with Horners have mitosis, ptosis, and andhydrosis.

They may also present with loss of pain and temperature sensations in the limbs and trunk contralateral to the lesion due to the proximity of the spinothalamic tract to the descending hypothalamic axons.

Question 6

Lesion of MLF

Answer 6

Lesions of the MLF may result in internuclear opthalmoplegia which disrupts horizontal conjugate gaze and the vestibuloocular reflex

*MLF particularly susceptible to CNS disease such as MS and neurosyphilis

Question 7

Oculomotor nerve lesions

Answer 7

All of the muscles that adduct the eyeball are innervated by CN III so a lesion may result in a laterally deviated eyeball (external strabismus) because of an inability to aDDuct eyeball

patients may have ptosis and parasympathetic deficits

preganglionic parasympathetic axons course in the peripheral part of CN III and are subject to external compression before the skeletal motor fibers. Initial signs of compression are therefore a dilated pupil, loss of the light reflex, and loss of the near response on the side of the lesion

Question 8

Hypoglossal Nerve lesion

Answer 8

results in an ipsilateral paralysis of one half of the tongue and a deviation of the tip of the tongue on protrusion toward the side of the lesion

Question 9

Glossopharyngeal nerve lesions

Answer 9

reduction in parotid secretions, difficult to use as diagnostic tool

Question 10

Trigeminal nerve lesions

Answer 10

unilateral lesion of the motor fibers of CN V may result in a deviation of the jaw on protrusion toward the side of the lesion

Question 11

Bell’s Palsy

Answer 11

lesions of the skeletal motor axons in the facial nerve may result in a complete paralysis of muscles of facial expression ipsilateral to the side of the lesion and hyperacusis due to weakness of stapedius

patients have weakness in the ability to wrinkle the forehead, shut the eye, flare a nostril, and show their teeth on the side of the lesion

Question 12

Vagus nerve lesion

Answer 12

a lesion of the motor axons of vagus that arise from the nucleus ambiguus may result in an ipsilateral weakness of the soft palate and a nasal regurgitation of liquids. The tip of the uvula may deviate away from the lesion

a weakness of the pharyngeal muscles may result in difficulty in swallowing (dysphagia) and a weakness laryngeal muscles may result in hoarseness.

Question 13

Lesions of the medulla

Answer 13

may affect fibers of CNs IX, X, or XII but not CN XI because the fibers of this arise from the cervical spinal cord

Question 14

Accessory nerve lesions

Answer 14

occurs commonly outside the skull and results in a weakness in the ability to laterally rotate the scapula during abduction and a weakness in the ability to elevate the scapula. Accessory nerve lesions may also result in a weakness in the ability to turn the chin to the side opposite the lesion

Question 15

Lesions of corticobulbar axons to the hypoglossal nucleus

Answer 15

the tongue muscles will not undergo fasiculations and atrophy and may deviate AWAY from the injured corticobulbar fibers (versus lesion of the hypoglossal nerve towards the injured side)

Question 16

in a lesion of the corticobulbar axons to the nucleus ambiguus

Answer 16

the uvula may deviate toward the lesions fibers (versus the vagus nerve lesion where it deviates away)

Question 17

Patients with facial weakness - how to distinguish

Answer 17

differentiate between a lesion of CN VII and a lesion of the corticobulbar fibers to the facial motor nucleus

Patients with a facial nerve lesion: may have a complete paralysis of muscles of facial expression ipsilateral to the side of the lesioned nerve and have an inability to wrinkle the forehead, shut the eye, and flare a nostril, and a drooping of the corner of the mouth

Unilateral corticobulbar lesion may result in only a lower face weakness as evidenced by a drooping of the corner of the mouth on the side of the face contralateral to the lesioned corticobulbar fibers. These patients will be able to wrinkle their forehead and shut their eyes and will have an intact blink reflex.

Question 18

bilateral lesion of the solitary nuclei

Answer 18

may cause respiratory failure (respiratory failure may by preceded by ataxic respiration)

Question 19

Gag reflex

Answer 19

uses visceral sensory fibers in CN IX and skeletal motor fibers in CN X

Question 20

Cough reflex

Answer 20

uses both sensory and motor fibers in CN X

Question 21

Tirgeminal Neuralgia (Tic Douloureux)

Answer 21

trigeminal neuralgia is characterized by episodes of sharp, stabbing pain radiating over the territory supplied by mucosal or cutaneous branches of the maxillary or mandibular divisions of the trigeminal nerve

pain is frequently triggered by moving the mandible, smiling, or yawning or by cutaneous or mucosal stimulation

Question 22

Conductive hearing losses

Answer 22

result from interference of sound transmission through the external ear or middle ear. Middle ear infections children and otosclerosis in adults are common causes of a conductive hearing loss.

In conductive hearing loss, bone conduction is better than air conduction as a result of loss of the amplification provided by the middle ear.

Patients with conductive hearing loss will hear the vibrations better on the side of the defective external or middle ear because vibrations that reach the normal ear by both bone and air conduction interfere with each other, making the normal ear less sensitive.

Question 23

Sensorineural hearing losses

Answer 23

result from a loss of hair cells in the cochlea or from a lesion to the cochlear part of CN VIII or to any CNS auditory structure

Question 24

4 common causes of a sensorineural hearing loss at the cochlear level:

Answer 24

trauma from high intensity sound

infections

drugs

prebycusis: most common cause of sensorineural hearing loss in the elderly and results from progressive high frequency hair cell loss near the base of the cochlea.

Question 25

Ipsilateral sensorineural hearing loss

Answer 25

the lesion is most likely in the inner ear, CN VIII, or cochlear nuclei but not at higher levels of the central auditory system which contain neural structures that receive inputs from both ears.

Question 26

Lesion to CNS auditory structures in the brainstem:

Answer 26

above the cochlear nuclei, in the thalamus, or in the cortex may result in a slight bilateral hearing loss and a decreased ability to localize a sound source.

Question 27

Vestibular lesion

Answer 27

patients may have vertigo, an abnormal perception of rotation which may involve either the subject or the external space. The vertigo is usually severe in peripheral vestibular lesions and mild in central CNS lesions.

Question 28

Meniere’s disease

Answer 28

patients may have abrupt, recurrent attacks of vertigo lasting minutes to hours. The vertigo may be accompanied by tinnitus and an ipsilateral sensorineural hearing loss. Nausea, vomiting, and a sensation of fullness or pressure in the ear also are common during the acute episode.

The disease usually occurs in middle age and results from distention of the endolymph-filled spaces in the cochlear and vestibular parts of the labyrinth

Question 29

Nystagmus

Answer 29

slow, rhythmic oscillation of the eyes to one side followed by a fast reflex movement of the eyes in the opposite direction

it is usually horizontal, although rotatory or vertical nystagmus may also occur.

it is defined by the direction of the fast, or corrective phase.

It may result from a lesion of the labyrinth, vestibular nerve, or nuclei. It may also result from a metabolic disease or a lesion of the cerebellum, visual system (usually reflex centers and their connections), or cerebral cortex.

Question 30

Pathologic Nystagmus involving the vestibular nerve

Answer 30

an initial slow deviation of the eyes toward the side of the lesion in response to the pathology. A fast or corrective phase occurs in the opposite direction that is generated by the cerebral cortex.

In patients with a vestibular-evoked nystagmus the fast or corrective phase is away from the side of the lesion. A peripheral nystagmus is usually accompanied by vertigo. In a central lesion of the vestibular nuclei or cerebellum, the nystagmus may be bidirectional and may occur without vertigo.

Question 31

Caloric testing

Answer 31

evaluates the vestibulo-ocular reflex by introducing warm or cool water into an external auditory meatus

the direction of the fast phase of vestibular evoked nystagmus in a caloric test toward the warm water side and away from the cool water side is summarized by the COW (cool - opposite - warm - same)

Question 32

Caloric testing and the comatose patient

Answer 32

in a comatose patient with a nonfunctioning cerebral cortex but an intact brainstem caloric testing will only generate a slow deviation of both eyes, but not a fast or corrective phase.

In a comatose patient with a bilateral MLF lesion above the abducens nucleus, caloric testing will only result in a slow deviation of the abducting eye because adduction requires that the MLF be intact.

in a patient with a bilateral lesion to the vestibular nuclei, there will be no eye movement at all in response to caloric testing.

Question 33

brainstem lesions deficits

Answer 33

commonly result in signs or symptoms that begin with letter “d”

diplopia

a deviated eye, tongue, uvula, or mandible

dysphagia

dysphonia

a drooping eyelid

droopy face

Question 34

thalamic pain syndrome

Answer 34

commonly results from a lacunar stroke involving thalamoperforating branches of a posterior cerebral artery, which supply the ventrobasal complex

patients may have an impairment of all forms of somatic sensations in the body and limbs contralateral to the affected thalamus

central pain may also occur if the lesion affects the anterolateral system part of the ventrobasal complex. Patients have an initial analgesia which is replaced over time by spontaneous aching, burning pain, which is often excruciating, and a heightened sensation of pain is felt even after light cutaneous stimulation of the contralateral limbs or body. There is frequently a heightened sensation of cold or heat.

Pain in thalamic pain syndrome will not respond to anti-inflammatoryy analgesics which act to suppress pain at brainstem or spinal cord levels4

Question 35

lesions of the supraoptic and paraventricular nuclei

Answer 35

may result in diabetes insipidus which is characterized by polydipsia (excess water consumption) and polyuria

-may also be due to trauma to the hypothalamohypophysial tract