Brainstem lesions review Flashcards
1
Q
What is the rule of four when solving brainstem lesions
A
- there are 4 structures in midline beginning with M.
- there are 4 structures to the side (lateral) beginning with S
- There are 4 cranial nerves in medulla 4 in pons, and 4 above the pons
- the 4 motor cranial nerve nuclei in midline are those that divide equally into 12 (except for 1 and 2) the is 3,4,6 and 12
2
Q
Medial brainstem vascular syndromes: typical presentation
A
- motor pathway: contralateal weakness
- medial lemniscus: contalateal loss of discriminative touch/vibation/conscious proprioception
- medial longitudinal fasciculus: ipsilateral internuclear opthalmoplegia (eye muscle paraylsis)
- Motor nucleus and nerve: ipsilateral loss of affected cranial (3,4,6,12)
3
Q
Lateral brainstem vascular syndromes
A
- spinalcerebellar pathway: ipsilateral ataxia
- spinothalamic: contalateral loss of pain and temperature
- spinal nucleus of trigeminal nerve CN 5: ipsilateral loss of pain and temperature frorm face
- sympathetic pathway: ipsilateral horners syndrome (partial ptosis and small pupil)
4
Q
Internuclear opthalmoplegia
A
- a lesion of the medial longitudinal fasciculus prevents abducens nucleus signals from reaching the contralateral oculomotor nucleus
- when the perrson attempts to voluntarily look to the right the left eye does not adduct
- she is attempting to look to her right but the left pupil does not adduct
5
Q
Lesions affecting eye movements
A
- medial brainstem lesions may damage CN 3 and 4 if in the midbrain and 6 if in the pons
- medial brainstem lesions at any level may damage the medial longitudinal fasciculus, resulting in an INO
6
Q
Horners syndrome
A
- a lesion of the sympathetic pathway to the face results in a drooping eyelid, pupil constiction, and dry red skin of the face
- normally activity in this sympathetic pathway dilates the pupil, constricts blood vessels in the face, activites sweat glands of the face and neck
- assists the levator palpebrae muscles in elevating the upper eyelid
7
Q
Important structures of the inferior medulla
A
- nucleus gracilis/cuneatus
- spinal nucleus of trigeminal nerve
- posterior spinocerebellar tract
- anterior spinocerebellar tract
- spinothalamic tract
- MLF
- medial lemniscus
- corticospinal tact in the pyramid
8
Q
Important structures of the upper medulla
A
- spinal nucleus of trigeminal nerve
- CN 12
- inferiorr cerebellar peduncle
- spinothalamic tract
- MLF
- trigeminal lemniscus
- medial lemniscus
9
Q
Important structures of
pons
A
- MLF
- anterior spinocerebellar tract
- middle cerebellar peduncle
- spinothalamic tract
- medial lemniscus
- corticopsinal, corticobainstem and corticopontine tract
- spinothalamic tract
- CN6
10
Q
important structures of
midbrain
A
- Superior colliculus
- oculomotor nucleus
- red nucleus
- substantia nigra
- CN 4
- inferior colliculus
- nucleus of tochlear nucleus
- MLF
- spinothalamic tract
- medial lemniscus
- oculomotor nerve
11
Q
midbrain tectum
A
- pretectal area: involved in pupillary consensual and accommodation reflexes of the eye
- inferior colliculi: involved in transmission of auditory information
- superior colliculi: involved in reflexes eye and head movement
12
Q
Disorders of the brainstem region
how to figure out to location of lesion
A
- evaluating function of CNs and vertical tracts can localize lesions within the brainstem
- single brainstem lesions may cause a mix of ipsilateral and contralateral signs
- occur becuase CNs supply the ipsilateral face and neck
- many of the vertical tracts cross midline in the brainstem to supply the contralateal body
- lesions in the brainstem may also interfere with vital functions and consciousness
13
Q
4 Ds of brainstem dysfunction
A
- dysphagia
- dysarthria
- dysmetria
- diplopia
- may also have disorders of vital functions: heart rate, blood pressure, respiration
14
Q
corticobrainstem tract lesions
A
- convey motor signals from cerebral cortex to CN nuclei in brainstem
- neurons with axons in the corticobrainstem tract serve as UMNs to the LMNs in CNs 5, 7, 9, 10, 11, and 12
- UMN tract lesions are assoicated with muscle hypertonia
- LMN lesions are assoicated with hyporeflexia and muscle flaccidity
15
Q
UMN vs. LMN fascial weakness
A
- complete lesions of NC 7 LMN cause ipsilateral paralysis of fascial muscles while lesions of corticobrainstem axons to the fascial nucleus cause contralateral lower face paralysis with sparing of control of upper face due to bilateral projections of corticobrainstem
