Lesions affecting brainstem function Flashcards
what are the parts of the brainstem
medulla oblongata
pons
pituitary gland
thalamus
(most pirates parrots talk)
where are the cranial nerves situated
cranial nerves are in the brainstem which is the part that enters the brain after the spinal cord
what are the cranial nerves
olfactory
optic
oculomotor
trochlear
trigeminal
abducens
facial
vestibular
glossopharnageal
vagus
accessory
hypoglossal
where do the cranial nerves lieT
The4 cranial nerves in the medullaareCN 9-12:
Glossopharyngeal (CN9): ipsilateral loss of pharyngeal sensation
Vagus (CN10): ipsilateral palatal weakness
Spinal accessory (CN11): ipsilateral weakness of the trapezius and stemocleidomastoid muscles
Hypoglossal (CN12): ipsilateral weakness of the tongueThe 12th cranial nerve is the motor nerve in the midline of the medulla. Although the 9th, 10th and 11th cranial nerves have motor components, they do not divide evenly into 12 (using our rule) and are thus not the medial motor nerves.
The4 cranial nerves in the ponsareCN 5-8:
Trigeminal (CN5): ipsilateral alteration of pain, temperature and light touch on the face back as far as the anterior two-thirds of the scalp and sparing the angle of the jaw.
Abducent (CN6): ipsilateral weakness of abduction (lateral movement) of the eye (lateral rectus).
Facial (CN7): ipsilateral facial weakness.
Auditory (CN8): ipsilateral deafness.The 6th cranial nerve is the motor nerve in the medial pons. The 7th is a motor nerve but it also carries pathways of taste, and using the rule of 4 it does not divide equally in to 12 and thus it is not a motor nerve that is in the midline. The vestibular portion of the 8th nerve is not included in order to keep the concept simple and to avoid confusion. Nausea and vomiting and vertigo are often more common with involvement of the vestibular connections in the lateral medulla.
The4 cranial nerves above the ponsareCN 1-4:
Olfactory (CN1): not in midbrain.
Optic (CN2): not in midbrain.
Oculomotor (CN3): impaired adduction, supradduction and infradduction of the ipsilateral eye with or without a dilated pupil. The eye is turned out and slightly down.
Trochlear (CN4): eye unable to look down when the eye is looking in towards the nose (superior oblique).The 3rd and 4th cranial nerves are the motor nerves in the midbrain.
what is the pyramidal tract
carries information from the brain to the muscle
fibres originate in the cerebral cortex carrying upper motor nerves fibres to the spinal cord
(corticospinal) and brainstem (corticiobulbar)
transmits signals for the voluntary control of the musculature of the body and the face
no synapses within descending pathways
upper motor neurone from brain then lower motor neurone to the muscle
where do fibres pass in the pyramidal tract
fibres pass from the cereal cortex to the brainstem and the spinal cords
they synapse to the lower motor neurones
what are cerebral penducels
two stalks which attaches the cererbrum to the brainstalk (largest portion of the brain the pink cloudy bit
located on the anterior part of the midbrain
contains the easending and descending nerve fibres between the brain and the brainstem
what is the red nucleus
lies within the midbrain
the red nucleus is pale pink due to the presence of iron
recievies inputs from the cerebellum of the opposite side
and the motor cortex of the same side
function = coordinate motor movement
what are the three types of brainstem lesions
three categories
nucelar
internuclear
infra nuclear - below the level of the nuclei
generally nuclear palsies are a rare occurrence
and often associated with other neurological signs because of other structures in close proximity
what is the difference between nuclear , internuclear and infranuclear lesions
nuclear - lesion at the level of the nucleus
internuclear pathway - between two nuclei - i.e. the third and 6th -
infra nuclear - affects nerve not brain - e.g. hypertensive/ diabetic
describe the contents of the oculomotor nerve
2 nuclei
oculomotor nerve nucleus - superior rectus , inferior rectus , and levator palpabrae superioris
2 types of efferent nerve fibres - somatic innervate the (eoms) and visceral innervate the (sphincter and cillary body) - parasympathetic
where does the third nerve enter and exit the skull
originates at the level of the midbrain (superior colliculus) and leaves the skull from the superior orbital fissure
inside the third nerve what is each muscle innervated by
each muscle is innervated by the corresponding sub nucleus
all subnuclei innervate ipsilateral muscles
except from the superior rectus sub nucleus and the central caudal nucleus
what does the central central caudal nucleus innverate
the levator palpable superior
what does a lesion at the central caudal nucleus result in
central caudal nucleus (CCN) supplies both levator muscles
lesion results in bilateral ptosis
with and without superior rectus limitation
if bilateral limitation of elevation
- lesion affecting superior rectus sub nucleus
what are fasicualr lesions of the third cranial nerve
fascicular = whilst the nerve is travelling within the brainstem
if there is a unilateral limitation of elevation not the superior rectus subnucleus
involvement of the superior reectus nerve fascicles (axons after leaving the nucleus)
because axons from 1 superior rectus subnuclueu cross and pass through cintrlaterla as well as ipsilateral subnucleus
describe the course of the trochlear nerve
originates in the midbrain
only cranial nerve to exit from the posterior midbrain
smallest cranial nerve (by number of axons)
longest intracranial course
unable to distinguish between nuclear and fascicular lesions
describe the course of abducens nerve (6th)
rginates in the lower pons in the floor of the fourth ventricle lateral to the medial longitudinal fasiculus
nerves exits at the junction of the medulla and the pons
it then courses over the medial petrous per towards the cavernous sinus
what are the 6 syndromes of the sixth cranial nerve
the brainstem syndrome
elevated intracranial pressure syndrome
the petrous apex syndrome
the cavernous syndrome
the orbital syndrome
the isolated 6th (microvascular) - petrous apex = raised intracranial pressure
what are the nuclear lesions of the 6th nerve palsiee
horizontal gaze palsy
ipsilateral lateral rectus and contrlateral medial rectus affected
this is because the 6th nucleus lies lateral to the medial lateral fasiculus
some neurones project to the medial lateral fasiculus
cross over to contralateral side and innervate contralateral medial rectus sub nucleus
what would a fascicular lesion of the 6th nerve result in
an ipsilateral lateral rectus palsy
what are the types of brainstem syndromes
webers syndrome
beendigst syndrome
fovilles syndrome
millard gubler syndrome
what can multiple cranial nerve involvement result in
can be caused by lesions such as
infarction haemorrhagage
tumour
deymyelination
trauma
what is colliers sighn
unilateral or bilateral eyelid retraction due to midbrain lesions
what is a characteristic feature of the dorsal midbrain syndrome
characteristic feature of the dorsal midbrain syndrome (Parinaud Syndrome) could be assessed on upward gaze palsy
convergence retraction nystagmus
convergence retraction nystagmus - upward and inward beating when own drum is postiioned downwards
bilateral lid retraction (colliers sign)
light near dissociation
what is webers syndrome
midbrain stroke syndrome
lesion in the midbrain affecting
3rd nerve fascicles
cerebral penducels
what are signs of webers syndrome
ipsilateral 3rd nerve palsy
contralateral hemiparesis - weakensss to one Side of the body
what is beneddikts syndrome
paramedian midbrain syndrome
lesion in the midbrain affects
3rd nerve fascicles
red nucleus
cerebral peduncle
what are signs of Benedikts syndrome
ipsilateral 3rd nerve palsy
contralateral hemiparesis
contralateral ataxia with hypeerkinesis/tremor
what is fovilles syndromee
lesion affects
abducens nucleus
ventral (anterior) pons
pyramidal tracts
what are signs of fovilles syndrome
ipsilateral 6th nerve nuclear palsy
ipsilateral horizontal gaze palsy
ipsilateral facial palsy
contralateral hemiparesis
what are signs of Millard gubler syndromees
lesion affects the base of pons anteroom medially affecting 6th and 7th nerve fascicles
pyramidal tracts
signs= espy;ateral 6th nerve palsy
ipsilateral facial nerve palsy (7th cranial nerve )
contralateral hemiplegia
what is divergence paralysis
poorly understood
theories=
a divergence centre in brainstem and around 6th nerve nucleus
lesion of cerebellum or Arnold chairi malformation -which is the blockage of cerebral spinal fluid
what are the signs of divergence paralysis
convergent deviation
homonymous diplo[ia
normal om- full abudction either eye
absent negative fusion amplitude
what is the ateioloy of divergence paralysis
aetiology raised ice , ms , encephalitis , trauma , miller fisher syndrome
what is the differential diagnosis for divergence paralysis
differential diagnosis= 6th nerve palsy
concomitant et
convergence spasm
treatment - may resolve on observation
occlude/ base out prisms
lateral rectus resections
what diseases affect brainstem ocular motility function
Parkinson’s disease- limited upgaze
Huntingdon’s disease
Wernicke’s encephalopathy
Whipple’s disease
Arnold-Chiari malformation
what is Parkinsons disease
Degenerative condition of CNS due to insufficient production of dopamine - mainly affects substantia nigra in BS
Causes: idiopathic (main), viral, inherited, trauma, drug induced
Rigidity, tremor, slow movements (cognition, mood and sleep can
also be affected)
Medication can help in short term but effect reduces over time and no cure
what are the features of Parkinson’s disease
Ocular features…
Limited upgaze
Downgaze might be affected later
Hypometric saccades
Convergence insufficiency
Nystagmus
Reduced control of phoria – diplopia
Impaired smooth pursuit
Blepharospasm
Lid lag
what is Huntingtons disease
Hereditary disorder of CNS
Substantia nigra in BS may be involved or pre-nuclear (e.g. Frontal eye fields or superior colliculus)
Loss of mobility, difficulty with speech and swallowing
Ocular features
Difficulty initiating saccades
Slow saccades
Impaired smooth pursuit
enlargement of the frontal horns
what is wernike - Korsakoff encephalopathy
Spectrum of disorder caused by thiamine (B1) deficiency
Common in alcoholics but can also occur in gastric disorders e.g. Crohn’s disease
Gait ataxia, confusion, impaired short term memory
Treat with thiamine injections but can progress to Korsakoff’s syndrome
what is the difference between wernike and Korsakoff
Wernicke (acute, reversible) - Korsakoff (chronic, irreversible)
what are the ocular features of wernicke - korsakoff encephalopy
Ocular features:
Weakness of abduction
Gaze-evoked nystagmus
INO
Vertical nystagmus
Horizontal/vertical gaze palsies
May progress to complete ophthalmoplegia
what is wipes disease
Caused by Tropheryma whippelii bacteria
Systemic disorder: weight loss, diarrhoea, gastro-intestinal bleeding, painful joints, arthritis, fever, fatigue, anaemia
Treated with antibiotics, although bacteria can remain in CSF
Can be fatal if left untreated
Ocular features
Reduced vertical saccades
Vertical and horizontal gaze palsies
Pendular oscillations
what is Arnold chiari malformation
Anomaly in which cerebellar tonsils are displaced downwards towards foramen magnum –base of skulland may herniate
Congenital or acquired
Headaches, neck pain, tinnitus, nausea, facial pain, muscle weakness, sleep apnea, difficulty swallowing, impaired co-ordination, rapid heart beat, dizziness, fainting, thirst, chronic fatigue, paralysis in severe cases
what are the ocular features of the Arnold chiari malformation
Ocular features
Various types of nystagmus but typically downbeat
Impaired pursuit
Impaired OKN
Concomitant ET
Divergence paralysis
Skew deviation
INO
