Nerve and Brain Lesions Flashcards
What are the nerve contents of most sensory nuclei?
Cell bodies of second order neurons
EXCEPTION: mesencephalic nucleus consists of cell bodies of first order neurons
Where are the cell bodies of most first order neurons for sensory cranial nerves?
Sensory ganglia of cranial nerves
Where do second order sensory neurons of cranial nerves usually synapse onto third order neurons?
Sensory nuclei of the thalamus (contralateral side)
Where are cell bodies of third order neurons for sensory cranial nerves?
Sensory relay nuclei of the thalamus
Where do axons of third order neurons in the sensory relay nuclei project?
To the primary sensory areas of the cerebral cortex (i.e. postcentral gyrus)
What is the effect of lesions of first order sensory neurons or the sensory nucleus? Lesions of the central pathway of sensory neurons?
First order/nucleus: ipsilateral sensory deficits (pre-decussation)
Central: contralateral sensory deficits (post-decussation)
Where do upper motor neurons synapse with lower motor neurons?
Motor nuclei
What is the most important upper motor neuron descending pathway?
Corticobulbar tract
What is the facial appearance of a lower motor neuron lesion in the brainstem or cranial nerves?
Ipsilateral flacid paralysis and loss of reflexes in full half of face
What is the facial appearance of an upper motor neuron lesion in the motor cortex and internal capsule?
Contralateral lower facial paralysis
contralateral because motor neurons for the lower half of the face cross, only lower because the upper face is supplied by neurons from both sides
What are the six cell columns of cranial nerve nuclei inthe spinal cord (listed medial to lateral)?
Somatic motor, parasympathetic, branchial motor, visceral sensory and taste, special sensory, and somatic sensory
What nerves are in the somatic motor column of the spinal cord?
- oculomotor nucleus (in midbrain at level of superior colliculus)
- trochlear nucleus (in midbrain at level of inferior colliculus)
- abducens nucleus (in midpons)
- hypoglossal nucleus (in medulla)
What nerves are in the parasympathetic column of the spinal cord?
Parasympathetic nerves from the oculomotor (Edinger-Westphal nucleus), facial (superior salivatory nucleus), glossopharyngeal (inferior salivatory nucleus), and vagus (dorsal motor nucleus) nerves
What nerves are in the branchial motor column in the spinal cord?
- trigeminal motor nucleus (rostral pons)
- facial motor nucleus (caudal pons)
- nucleus ambiguous (IX, X in the medulla)
- accessory nucleus (cervical cord)
What nerves are in the taste and visceral sensory column of the spinal cord?
Taste: rostral solitary or gustatory nucleus (VII, IX, X) in the medulla
Visceral sensory: caudal solitary nucleus (IX, X) in the medulla
What nerves are in the special sensory column of the spinal cord?
Vestibular and cochlear nuclei in the rostral medulla and caudal pons
What nerves are in the somatic sensory column of the spinal cord
What is the presentation of a hemisphere (supranuclear lesion)?
Interrupts both ascending and descending spinal and cranial nerve pathways –> body and face deficits contralateral to the injury
What is the effect of a supranuclear lesion on the uvula, tongue, sternomastoid, and trapezius?
Tongue deviates away from the lesion, uvula deviates towards the lesion (because the fibers are crossed to these muscles and the force vectors control the direction of deviation)
Ipsilateral weakness in sternomastoid and trapezius
What is the result of a brainstem (nuclear) lesion?
Damage to cranial nerve nuclei, ascending spinal cord (medial lemniscus and spinothalamic tract), and descending motor pathways (corticospinal tract)
Causes ipsilateral cranial nerve deficits and contralateral hemiparesis and various sensory deficits
location of the lesion (medulla vs. pons vs. midbrain and medial vs. lateral) determines what nuclei/pathways are damaged
What is the cause of medial medullary syndrome?
Occlusion of a branch of either the vertebral or anterior spinal arteries
What are the deficits caused by medial medullary syndrome?
Alternating hypoglossal hemiplagia: contralateral hemiparesis (corticospinal tract) and tactile/kinesthetic deficits (medial lemniscus); ipsilateral flaccid paralysis of the tongue (difficulty swallowing, speaking, and deviation)
What is the cause of lateral medullary (Wallenberg’s) syndrome?
Occlusion of the posterior inferior cerebellar artery (PICA)
What deficits are associated with lateral medullary (Wallenberg’s) syndrome?
- contralteral loss of pain and temperature from the body (spinothalamic tract)
- ipsilateral loss of pain and temperature from the face (spinal nucleus and tract of V)
- ipsilateral Horner’s syndrome (descending autonomic hypothalamospinal fibers)
- nystagmus, naseua, vomiting (vestibular nuclei and connections)
- ipsilateral limb ataxia (cerebellar connections)
- difficulty swallowing, hoarseness, and difficulty breathing + loss of gag reflex
- ipsilateral loss of taste or ageusia (solitary nucleus and tract)
What is the cause of ventral (Weber’s) syndrome of the midbrain?
Occlusion of a branch of the posterior cerebral artery
What deficits are associated with ventral (Weber’s) syndrome of the midbrain?
Contralateral hemiparesis (corticospinal tract) and ipsilateral oculomotor nerve palsy, paralysis of medial and upward eye movement, eyes turned down and out, drooping of eyelid, and pupillary dilation
A 65-year-old man presents with a history of progressive weakness of the muscles of mastication, some difficulty swallowing accompanied by rather raspy speech and difficulty speaking. A definite weakness of facial expression is present. What cranial nerve cell column is he suffering from lesions to?
a) general sensory
b) branchial motor
c) parasympathetic
d) somatic motor
e) special sensory
b) branchial motor
An upper motor neuron lesion of the facial nerve is produced by interrupting the corticobulbar fibers from the facial motor nucleus. Such a lesion on the left side of the brain will produce:
a) complete paralysis of the left side of the face
b) only paralysis of the left lower face
c) complete paralysis of the right side of the face
d) only paralysis of the right lower face
e) no paralysis at all because the corticobulbar fibers are both crossed and uncrossed
d) only paralysis of the right lower face
A patient is seen who has paralysis of the right upper and lower face caused by a stroke of the facial motor nucleus. Additionally, he has a loss of pain and temperature over the right side of the face and left side of the body (alternating hemianesthesia). His lesion is probably located in the:
a) left lateral pons
b) right lateral medulla
c) right lateral pons
d) left lateral medulla
e) right posterior limb of the internal capsule
c) right lateral pons
A patient presents with right hemiplegia of the arm and leg combined with a right lower facial paralysis, and sensory deficits in the right face, arm, and leg. Where is the most likely location of the stroke?
a) left posterior limb of the internal capsule near the genu
b) left middle cerebral artery
c) right posterior limb of the internal capsule near the genu
d) right middle cerebral artery
e) left middle and anterior cerebral arteries
a) left posterior limb of the internal capsule near the genu
A lateral lesion in the brainstem, as occurs in the lateral medullary syndrome, will damage which of the following cranial nerve nuclei?
a) hypoglossal nucleus
b) trochlear nucleus
c) abducens nucleus
d) oculomotor nucleus
e) spinal nucleus of V
e) spinal nucleus of V
What structures are most easily visible on a T1 MRI?
tissues with a fast T1 relaxation time - fat or subacute hemorrhage - will appear brighter than other tissues
What do MR angiograms do?
They allow for visualization of blood flow
What is the difference between anatomic vs. functional vs. molecular imaging?
anatomic imaging = basic diagnostic radiology
functional imaging = advanced diagnostic imaging
molecular imaging = more granular advanced diagnostic imaging on a cellular, genetic, or protein level
What is diffusion-weighted imaging?
A technique that quickly takes images and can detect acute ischemic brain infarction within minutes by identifying “dead zones” of underperfused regions that are more viscous
What is diffusion tensor imaging?
A type of imaging that reveals signal differences and can map out the white matter tracks of the brain
useful for brain tumor resection surgery
What is perfusion weighted imaging?
Imaging technique that allows for measurement of the level of cerebral blood flow
What is cerebral blood flow?
overall net blood delivery to brain, capillary flow
What is mean transit time?
Temporal information, time blood spends in capillaries
What is cerebral blood volume?
A view of resting auto regulation, amount of blood in the cerebral capillaries and veins
What are the imaging characteristics of phase I of the brain’s response to ischemia?
Increase in oxygen extraction fraction - minimal to no change appreciated with imaging
What are the imaging characteristics of phase II of the brain’s response to ischemia?
More severe hypoperfusion - leads to increased cerebral blood flow and prolonged mean transit time
What are the imaging characteristics of phase III of the brain’s response to ischemia?
Autoregulatory mechanisms fail - cell death occurs
cerebral blood volume falls
What is functional brain mapping (fMRI)?
An MRI that employs blood oxygen dependent pulse sequences that can perform scans before and after a clinical test and measure local changes in cerebral blood flow
