Brainstem & cerebellum Flashcards
Pseudobulbar affect
Uncontrollable bouts of laughter or crying without feeling the usual associated emotions caused by abnormal reflex activation of laughter & crying in the brainstem
Lesions of the optic nerve result in
Monocular visual loss or monocular scotomas; can be partial
Hypertropia
Abnormal vertical deviation of one eye
What are the most common causes of acute ataxia in children?
Accidental drug ingestion, varicella-associated cerebellitis, migraine
One-and-a-half syndrome
Ipsilateral internuclear ophthalmoplegia plus ipsilateral lateral gaze palsy (only mvmt unaffected is CL lateral rectus) Caused by lesions to the MLF + adjacent abducens nucleus OR MLF + PPRF
How is the trigeminal nerve examined?
Light touch, pain by pinbrick, hot/cold, corneal reflex, jaw reflex, jaw movements
What are the most common causes of chronic ataxia in adults?
Brain metastases, chronic toxin exposure, MS, degenerative disorders
Bulbar palsy
Dysarthria, dysphagia, & hypoactive jaw/gag reflex not associated with cognitive changes (pseudo is)
Ptosis
Drooping of eyelid
Infarcts that involve both the lateral brainstem & the cerebellum are most likely in what vascular territories?
PICA & AICA
A complete lesion of the cavernous sinus results in
Total ophthalmoplegia + fixed, dilated pupil
Brainstem controlling centers for vertical eye mvmts are located in the
Rostral midbrain reticular formation & pretectal area
Middle cerebellar peduncle
Brachium pons; connects to pons; carries mainly inputs
What is the function of the lateral cerebellar hemispheres?
Motor planning for extremities
Where do cerebellar output pathways cross?
1) as they exit in decussation of superior cerebellar peduncle 2) as corticospinal & rubrospinal tracts descend to spinal cord
CN X
Vagus; parasympathetics to heart, lungs, digestive tract; pharyngeal & laryngeal muscles; taste from epiglottis & pharynx
Ataxia-hemiparesis
Syndrome in which patients have a combo of unilateral UMN signs & ataxia, usually affecting the same side; often caused by lacunar infarcts, most often in corona radiata, IC, or pons
UMN vs LMN lesions of CN VII (facial)
UMN - spares forehead; LMN - affects entire half of face
Appendicular apraxia
Ataxia on movement of the extremities; caused by lesions of the intermediate & lateral portions of the cerebellar hemisphere, which affects the lateral motor systems
Function of the caudal reticular formation
Maintains important motor, reflex, & autonomic functions
The superior cerebellar artery supplies what structures?
Upper lateral pons, superior cerebellar peduncle, most of superior half of cerebellar hemispheres
Horner’s syndrome
Ptosis, miosis, anhidrosis Caused by loss of sympathetic innervation
Benign anisocoria
Slight pupillary asymmetry in 20% of the general population
The posterior inferior cerebellar artery supplies what structures?
Lateral medulla, most of inferior half of cerebellum, inferior vermis
The anterior inferior cerebellar artery supplies what structures?
inferior lateral pons, middle cerebellar peduncle, strip of ventral cerebellum
Paramedian pontine reticular formation (PPRF)
Important horizontal gaze center that provides input from cortex & other pathways to abducens nucleus
Parinaud’s syndrome
Impairment of vertical gaze, large & irregular pupils w/ light-near dissociation, eyelid abnormalities, impaired convergence
Smooth pursuit
Slower eye mvmts, not under voluntary control, allow stable viewing of moving objects
Common causes of internuclear ophthalmoplegia
MS plaques, pontine infarcts, MLF neoplasms
What is the most commonly injury cranial nerve in head trauma?
Trochlear
CN XI
Accessory; innervates the sternomastoid & upper part of trapezius muscle
Esotropia
Abnormal medial deviation of one eye
CN XII
Hypoglossal; innervates intrinsic muscles of the tongue
CN IX
Glossopharyngeal; motor to salivary glands & muscles of pharynx; sensory from posterior 1/3 of tongue, pharynx, middle ear
Locked-in syndrome
Large pointine lesions disrupt bilateral corticospinal tracts & abducens nuclei, eliminating body mvmts & horizontal eye mvmts
CN VIII
Vestibulocochlear; hearing & vestibular sensation
Oculomotor palsy
Paralysis of all extraocular muscles except lateral rectus & superior oblique (eye is “down and out”), upper lid is closed, pupil is dilated & unresponsive to light
Ataxia
Disordered contractions of agonist & antagonist muscles, lack of normal coordination between movements at different joints seen with cerebellar dysfunction
Trigeminal neuralgia (tic douloureux)
Recurrent episodes of brief pain in the distribution of the trigeminal nerve
What is the function of the cerebellar vermis & flocculonodular lobe?
Proximal limb & trunk coordination, balance & vestibulo-ocular reflexes
What are the most common causes of chronic ataxia in children?
Cerebellar astrocytoma, medulloblastoma, Friedreich’s ataxia, ataxia-telangiectasia
Lesions to the PPRF lead to
Ipsilateral lateral gaze palsy
Marcus Gunn pupil
Afferent pupillary defect; the direct response to light in the affected eye is decreased/absent while consensual response of the affected eye to light in the opposite eye is normal Caused by decreased sensitivity to light secondary to lesions of optic nerve, retina, or eye
Accommodation response
Occurs when a visual object moves from far to near, involves pupillary constriction, accommodation of the lens ciliary muscle, and convergence of the eyes
Argyll Robertson pupil
Light-near dissociation (pupil accommodates but doesn’t react to light) plus small & irregular pupils; associated with neurosyphilis
Bilateral acoustic neuromas are associated with
Neurofibromatosis Type 2
Pseudobulbar palsy
Used to describe dysarthria & dysphagia caused by UMN lesions in corticobulbar pathways (e.g., frontal lobe) not the brainstem; is associated with cognitive changes
Pupillary effects of opiate use
B pinpoint pupils
True vertigo
Spinning sensation of mvmt that is caused by lesions anywhere in the vestibular pathways
Friedrich’s ataxia
Hereditary (excessive trinucleotide repeats), progressive gait ataxia Speech may be affected, but cognition intact; emotional lability may be present
Right-way eyes
Cerebral hemisphere lesions normally impair eye mvmts in the CL direction, resulting in gaze preference toward sign of lesion, way from side of weakness
Symptoms of vagus nerve damage
Hoarseness, poor swallowing, loss of gag reflex
Exotropia
Abnormal lateral deviation of one eye
Medial longitudinal fasciculus (MLF)
Interconnects III, IV, VI, X nuclei
Pupillary effects of barbiturate overdose
B small pupils
Caloric test
Test of vestibulocochlear function that involves irrigating the ear
Which cranial nerves are located in the pons?
5-8
Effects of damage to the abducens nerve versus the abducens nucleus
Nerve - impaired abduction of IL eye Nuclei - IL gaze palsy in both eyes
Inferior cerebellar peduncle
Restiform body; connects to medulla; carries mainly inputs
Early symptoms of acoustic neuroma
Hearing loss, tinnitus, unsteadiness
Divisions of the trigeminal nerve
Ophthalmic, maxillary, mandibular
Trochlear palsy
Causes vertical dipolopia & hypertropia (eye is up & in)
Supranuclear pathways
Involve brainstem & forebrain circuits that control eye mvmts through connections with CN III, IV, & VI
Which cranial nerves are located in the medulla?
9-12
CN V
Trigeminal; general sensation for face, mouth, anterior 2/3rds of tongue; muscles of mastication & tensor tympani muscle
CN VII
Facial; motor for facial muscles, most salivation, anterior 2/3 tongue taste
What is the typical presentation of a cerebellar stroke?
Vertigo, nausea & vomiting, horizontal nystagmus, limb ataxia, unsteady gait, HA
What is the function of the intermediate cerebellar hemispheres?
Distal limb coordination
Ciliary muscle
Adjusts thickness of lens in response to viewing distance
What are the most common causes of acute ataxia in adults?
toxin ingestion, ischemic or hemorrhagic stroke
Function of the rostral reticular formation
Maintains alert conscious state in brain
Nuclear & infranuclear pathways
Involve brainstem nuclei of III, IV, & VI; the peripheral nerves arising from these nuclei, & the eye mvmt muscles
Damage to glossopharyngeal nerve leads to
spasms of pain in posterior pharynx
Pupillary effects of anticholinergic agents
Dilated pupils
Wrong-way eyes
Eyes look toward side of weakness; possible causes include seizure activity, large lesions such as thalamic hemorrhage, lesions of pontine basis & tegmentum
CN III
Oculomotor; innervates all extraocular muscles, except superior oblique & lateral rectus; also controls pupillary constriction & accommodation reflex
Internuclear ophthalmoplegia
Eye ipsilateral to lesion does not fully adduct on attempted horizontal gaze, nystagmus in opposite eye
CN VI
Abducens; innervates lateral rectus muscle, causes abduction of eye (turns eye out)
Sensory ataxia
Occurs when posterior column-medial lemniscus pathway is disrupted, resulting in loss of joint position sense
UMN vs LMN damage to CN XII (Hypoglossal)
UMN = CL tongue weakness LMN = IL tongue weakness
Herpes zoster causes sensory loss in the distribution of what cranial nerve?
V - trigeminal
Saccades
Rapid eye mvmts that bring target of interest into field of view
Conductive vs. sensorineural hearing loss
Conductive = abnormalities of external auditory canal or middle ear Sensorineural = disorders of cochlea or 8th nerve
Superior cerebellar peduncle
Brachium conjunctivum; connects to midbrain; carries mainly outputs
CN IV
Trochlear; innervates superior oblique muscle, causes depression & intorsion of eye
Common causes of oculomotor palsy
Diabetic neuropathy, head trauma, intracranial aneurysms, tentorial herniation, ophthalmoplegic migraine in children
Truncal ataxia
Wide-based, unsteady “drunklike” gait; caused by lesions in the vermis, which primarily affect the medial motor systems
Orbital apex
Region where nearly all nerves, arteries, & veins of the orbit converge before communicating with the intracranial cavity via the optic canal & superior orbital fissure
Bell’s palsy
unilateral paralysis of the muscles supplied by the facial nerve
