Neurosurgery Cortex Flashcards
what is the function of the corticobulbar tracts
contains UMN of the cranial nerves to provide innervation of the face, head and neck
they innervate the cranial motor nuclei bilaterally
(except the hypoglossal nuclei and the lower facial nuclei which are innervates contralaterally only)
explain the differences between a UMN and LMN facial paly
7th CN nucleus in pons
upper half of nucleus= upper half of face and same for lower and lower
upper half of nucleus receive motor input bilaterally, lower half of nucleus recieves only contralateral info
UMN will have paralysis of contralateral lower facial muscles with forehead sparing (as info from other side)= central facial palsy
LMN will have paralysis of the ipsilateral half of the face= bells palsy
what tracts originate from the brainstem and control involuntary movements
extra-pyramidal
- vestibulospinal
- reticulospinal
- rubrospinal
- tectospinal
what is the role of the vestibulospinal tract, and where does it originate
originates from the vestibular nucleus in the pons
it controls balance and posture by innervating the antigravity muscles (extensor for legs, flexor for arms)
what is the origin and function of the reticulospinal tract
Originates from the reticular formation in the medulla and pons:
The pontine reticulospinal tract facilitate voluntary/reflex responses and increases tone.
The medullary reticulospinal tract inhibits voluntary/reflex responses and decreases tone (think dulling down)
what is the origin and function of the rubrospinal tract
Originates from the red nucleus in the midbrain. It excites flexor muscles and inhibits extensor muscles of the upper body.
what is the origin and function of the tectospinal tract
Originates from the superior colliculus in the midbrain. It co-ordinates movements of head and neck to vision stimuli.
how many vertebrae all together
33
what does C1 lack
a spinous process or body
what is different about C2
has dens (ondontoid process)
what is different about C3-4
have short and bifid spinous processes
where does the posterior ligament run
within vertebral canal, posterior to the vertebral bodies
what does the ligamentum flavum do
It runs vertically connecting the lamina of adjacent vertebrae. It helps maintain an upright posture and assist straightening the spine after flexion.
where are LP done
L3/4
L4/5
what are the layers a needle has to go through in an LP
skin fascia supraspinous lig interspinous lig ligamentum flavum epidural space dura
what is the usual age range for mechanical back pain
20-55
when is mechanical back pain worse
morning stiffness which resolves with movement
pain is made worse by prolonged sitting or when rising from a seated position
what can happen when facet joints are hypertrophied
patients will get referred pain from the nerve supplying the facet join that mimics sciatica, but doesn’t radiate below the knee
describe a paramedian prolapse
aka posterolateral
most common
compresses travering disc
describe a far lateral prolapse
aka extraforaminal
compress the exiting nerve
what can a central/ medial herniation cause
lumbar stenosis or if large enough CES
what is radiculopathy
dysfunction of a nerve root causing dermatomal sensory deficit with weakness of the muscle groups supplied by the nerve
what is sciatic pain like
Shooting pain radiating from the buttocks down to the posterior knee/leg. The pain can be exaggerated by coughing or sneezing.
what does a straight leg raise test positive mean
with the patient lying down on their back, lift the patient’s leg while the knee is straight. If the angle to which the leg can be raised before eliciting the patient’s sciatic pain is <45° then the test is said to be positive.
what are the clinical features of an L5/S1 prolapse disc involing S1 root
Pain along the posterior thigh with radiation to the heel.
Weakness of plantar flexion (on occasion).
Sensory loss in the lateral foot.
Reduced or absent ankle jerk.
what are the clinical features of an L4/5 prolapse affecting L5
Pain along the posterior or posterolateral thigh with radiation to the dorsum of the foot and great toe.
Weakness of dorsiflexion of the toe or foot.
Paraesthesia and numbness of the dorsum of the foot and great toe.
Reflex changes unlikely.
what are the clinical features of an L3/4 prolapse affecting L4
Pain in the anterior thigh.
Wasting of the quadriceps muscle.
Weakness of the quadriceps function and dorsiflexion of foot.
Diminished sensation over anterior thigh, knee and medial aspect of lower leg.
Reduced knee jerk.
what are the indications for a discectomy following a prolapse
Failure of conservative treatment (physiotherapy and analgesia) - First line management
Pain
Central disc prolapse: Patients with bilateral sciatica or other features indicating a central disc prolapse, such as sphincter disturbance and diminished perineal sensation, should be investigated promptly.
Tumour
Neurological deficits
if what reflex is present does it make it unlikely to be CES
ankle
Tx for CES
emergency MRI lumbosacral
PR
If it was due to a herniated disc –> discectomy
If it was due to a fracture –> decompression +- fixation
If it was due to a hematoma –> evacuation
what are the clinical features of spinal stenosis
Unilateral or bilateral hip, buttocks or lower extremity pain or burning sensation precipitated by standing or back extension and relieved by sitting, lumbar flexion or walking uphill (patients can often develop an “anthropoid posture” which is exaggerated flexion of the waist).
Neurogenic intermittent claudication: leg weakness, tingling and numbness which can be accompanied by paresthesia.
insidious progressive disease
what is sclerotomal
muscle group with the same vascular supply (distribution of symptoms in vascular claudication)
what is the difference in pain in neural and vascular claudication
neural- burning
vascular- cramping
what investigation to diagnose neurogenic claudication
MRI lumbosacral spine
what is the treatment for neurogenic claudication
If symptoms are tolerable and the walking distance is not significantly affected then conservative treatment is offered first (physiotherapy and analgesia). Symptoms usually worsen slowly in a predictable manner and surgery should be offered electively when the patient’s symptoms become intolerable and oral analgesia is no longer sufficient. Lumbar surgical decompression (lumbar laminectomy) is the preferred surgical treatment.
what is cervical spondylosis and how can it present
a degenerative arthritic process involving the cervical spine
mainly >50s
either present as degenerative cervical myelopathy (UMN signs) or radiculopathy (LMN signs).
what is seen radiologically in cervical spondylosis
Narrowing of the disc space (the C5/C6 and C6/C7 levels are the most commonly affected)
Osteophyte formation
what is the Tx for cervical spondylosis
surgery:
- decompressive cervical laminectomy
- discectomy
- cervical foraminotomy
what causes myeopathy and what is the result
can result from a spinal cord compression which causes UMN signs with symptoms more prominent in the lower limbs
what are the clinical features of degenerative cervical myelopathy
older patients
progressive
imbalance and disturbance of gait/ falls (due to hypertonia and decreased proprioception)
clumsy hands
incontinence (rare)
non dermatomal pain
jumping legs at night due to hyperreflexia
weakness, spasticity
+ve babinski and hoffmans
what imaging for degenerative cervical myelopathy
MRI gold standard
- disc degeneration
- ligament hypertrophy
- spinal cord signal chance
Tx for degenerative cervical myelopathy
decompressive spinal surgery (prevent deterioration)
what is anterior cord syndrome
Cord infarction by the area supplied by the anterior spinal artery.
It produces paralysis and loss of pain and temperature below the level of injury with preserved proprioception and vibration sensation.
where does the contralateral loss of pain and temp begin in brown sequard
1 or 2 segments below the lesion
what causes central cord syndrome
Acute extension injury to already stenotic neck or syringomyelia or tumour
what are the symptoms of central cord syndrome
Predominantly bilateral upper limb weakness>lower limb (the fibers supplying the upper limbs in the lateral corticospinal tracts are more medial to the fibers supplying the lower limbs, hence a lesion in the central cord is more likely to damage the upper limb fibers).
“Cape-like” spinothalamic sensory loss (pain and temperature).
Dorsal Columns preserved.
how do you remember what rubrospinal tract does
think of a bro flexing his biceps
-excites flexors, inhibits extensors of the upper limb
explain decorticate vs decerebrate postures
Corticospinal most dominant motor tract, then ruborospinal
When don’t have corticospinal tract innervation, rubro will take over (flexion of upper limbs)= decorticate
When rubro knocked out reticulo happens (extension of upper and lower limbs)= decerebrate
what posture will result from a lesion above the level of the midbrain
decorticate- rubrospinal in tact as red nucleus in midbrain, cortico not working
what posture will result from a lesion below the midbrain
decerebrate = cortico and rubro tracts not working so reticulo (originates in pons/ medulla) takes over
how does the DCML reach the post central gyrus
decussate in medulla to the contralateral medial leminiscus to reach the primary somatosensory area
describe the 3 order neurones in the DCML
1st order neurone travel from site of excitation to dorsal sensory ganglion in spinal cord root. 2nd enters dorsal column and ascend entirety of cord crossing to the other side then thalamus where it synapses. 3rd – thalamus to post central gyrus
A 30 year old man presented with a stab wound in his back. He has right sided weakness starting at T5 and left sided loss of pinprick sensation and temperature starting at T7.
what cord compression syndrome
brown sequard
A 39-year-old woman presented with severe headaches whenever she sneezed. She also had decreased sensation to pinprick over her upper back, shoulders, and upper arms. Her power in her arms was 2/5 but her lower body power was 5/5.
what spinal cord compression syndrome
syringomyelia (type of central cord syndrome)
what is syringomyelia
when a cysts forms on the spinal cord and compresses it
what are the dural venous sinuses
between the two layers of dura mater
what is the outer layer of dura mater adherent to
periosteum
what is the cerebellum derived from embryologically
telencephalon
what does the middle frontal gyrus in the frontal lobe do
contains the frontal eye fields which control contralateral voluntary eye movements
what does the inferior frontal gyrus in the frontal lobe do
contains bocas speech area (in the dominant hemisphere)
what does damage to brocas area produce
expressive dysphagia
can comprehend words but produce faulty sentences and phonemic errors
what does damage to the inferior parietal lobule cause
nominal aphasia (problems recalling words, names and numbers
what does the superior temporal gyrus contain
the auditory area of the cortex
wernickes speech area (in dominant hemisphere)
what does damage to wernickes area cause
receptive dysphasia - impaired comprehension, produces jargon ‘word salad) but speech fluent
where is the visual cortex
occipital lobe
where is the insula
lies deep within the lateral sulcus
what is the role of the limbic system
higher emotional functions
contains major component of the memory system
where is the limbic system
medial hemisphere surface, encircles the corpus callosum
important structure include the cingulate gyrus and the hippocampus
what is the cerebellum derived from embryologically
the metencephalon
what separates the cerebrum from the cerebellum
tentorium cerebelli
what is the vermis
midline structure which connects the two hemispheres of the cerebellum
what are the three components of the cerebellum and their functions
vestibulocerebellum - receives input from the vestibular organs for the maintenance of balance and coordinating vestibule-ocular reflexes
spinocerebellum- maintains muscle tone and participates in posture and gait
cerebrocerebellum- coordination of voluntary motor activity, corrects any error in the movements to ensure they are smoothly executed
what is scanning dysarthia
when a patient speaks slowly with poor articulation of speech - caused by cerebellar dysfunction
what parts of brain are derived from the diencephalon
thalamus
hypothalamus
subthalamus
epithalamus
what does the thalamus do
involved in maintaining consciousness
modulates motor function- has reciprocal connections with the motor cortex, basal ganglia and cerebellum
is a relay station for all all sensory impulses (e.g. lateral geniculate nucleus is a relay between retina and visual cortex)
what can a thalamic infarction cause
hemiparesis, spontaneous pain, hemichorea, severe impairment of consciousness
what does the hypothalamus do
influences autonomics, endocrine and limbic system
- thermal regulation
- regulates release of hormones from adenohypophysis
- synthesis ADH and oxytocin (projects to the neurohypophysis)
- regulates feeding and starvation
- contains mamillary nucleus which receives information from the hippocampal formation
what nucleus is affected in wernickes encephalopathy
mamillary nucleus
what deficiency causes wernickes
B1 (thiamine)
what characterises korsakoffs
anterograde amnesia and confabulation
how do patients with wernickes present
confusion, ataxia and nystagmus
what do subthalamic lesions cause
contralateral hemiballism (chorea)
subthalamus is closely connected to the basal ganglia
what does the basal ganglia contain
caudate nucleus, putamen and globus pallidus
what is the role of the basal ganglia
exert both excitatory and inhibitory effects of the motor cortex
initiate and facilitate movement
control muscle tone
what do lesions in the basal ganglia cause
alteration in muscle activity or tone
what are alpha-synuclein containing inclusions
lewey bodies
present in parkinsons
what gene causes huntigtons
CAG trinucleotide repeats - increase from generation to generation (genetic anticipation)
what five different symptoms do tumours of the CNS present with
progressive focal neurological deficits
HA- worse on lying down, associated with N&V due to increase ICP
seizures
gradual cognitive slowing and personality changes
endocrine disturbances in pituitary or hypothalamic tumours
what symptoms might a lesion in the frontal lobe cause
contralateral weakness (motor cortex)
personality changes
urinary incontinence (micturition inhibition centre)
gaze abnormalities (frontal eye fields)
expressive dysphagia/ aphasia (brocas area)
seizures
what symptoms might a lesion in the temporal lobe cause
memory deficits
receptive aphasia/ dysphagia (wernickes area)
contralateral supeiror quadrantopia
seizures
what symptoms might a lesion in the parietal lobe cause
contralateral weakness and sensory loss (primary somatosensory cortex)
contralateral inferior quadrantopia
if domininant lobe affected: dyscalculia, dysgraphia, finger agnosia, left and right disorientation
if non dominant lobe affected: neglect (deficit in awareness of one side of body), dressing apraxia and constructional apraxia
what symptoms might a lesion in the occipital lobe cause
contralateral homonymous hemianopia
visual hallucinations
what symptoms might a lesion in the cerebellum cause
ipsilateral ataxia N&V dizziness and vertigo slurred speech intention tremor
what is the WHO grading for gliomas
I- no morphological features
II- atypia alone
III- atypia and mitosis
IV- atypia and mitosis with vascular proliferation/ necrosis
what is the most common primary brain tumour
high grade gliomas
what are high grade gliomas
either WHO grade II (anaplastic astrocytomas) or grade IV glioblastoma multiforme (GBM)
of these GBM more frequent
who gets glioblastoma multiforme tumours
older people
where do GBM tumours arise
in cerebral hemispheres - most commonly in temporal, parietal and frontal lobes
what imaging for glioblastomas
MRI
seen as heterogeneously enhancing SOL, with areas of necrosis, can have a butterfly appearance
what is done if an MRI shows a high grade glioma
biopsy taken for prognosis and MGMT promoter and methylation test (predictive repsonse alkylating agent chemo (temozolamide)
what is the treatment for gliobastomas
Stupp protocol:
-surgery + radiotherapy +/- chemo (e.g. temozolamide)
can improve median survival to 14 months
what are low grade gliomas
slow growing primary brain tumours grades I (pilocytic astrocytomas) and II (diffuse astrocytoma/ oligodendrogliomas)
who gets low grade gliomas
children and adults
most common in 2nd and 3rd decades
who gets pilocytic astrocytomas (a type of low grade glioma)
children and young adults
what is the prognosis for a pilocytic astrocyoma
high cure rate after maximal resective surgery +/- adjuvant therapy
what is the most common low grade glioma
pilocytic astrocytoma
what is the histology of a pilocytic astrocytoma
bipolar cells with long hair like projections
where do pilocytic astrocytomas occur
cerebellum and midline structures (thalamus, optic chiasm)
what condition are optic pathway gliomas common in
neurofibromatosis type 1
where do you get diffuse astrocytomas
cerebral hemispheres, esp frontal and temporal lobes
who gets a diffuse astrocytoma and how do they present
young adults
are slow growing - can progress to higher grades
commonly present with seizures
what is the treatment for diffuse astrocytomas
maximal resective surgery + chemo/ radiotherapy
can double life expectancy to beyond 15 years
which low grade glioma has the best prognosis
oligodendrogliomas
where do you get oligodendrogliomas
affect the frontal lobe of the cerebral hemisphere, white matter, cortex
can invade subarachnoid space
who gets oligodendrogliomas and how do they present
25-45 y/o’s
seizures and headaches
what are meningiomas
common benign extra-axial
(external to brain parenchyma) intracranial tumours that grow slowly, are well demarcated and do not usually infiltrate the brain
(originate from arachonid cap cells in arachoid membrane)
who gets meningiomas
elderly patients - 6th/7th decade
females slightly more
NF type 2
childhood radiation exposure
how do meningiomas present
usually asymptomatic and are found incidentally on imaging
if symptoms develop, then it will correlate with the site of the brain that is affected. The most common presenting complaint however is headache then symptoms of increased intra-cranial pressure can follow.
A meningioma in the olfactory groove can lead to Foster Kennedy syndrome which is clinically defined as optic atrophy in the ipsilateral eye and papilloedema in the contralateral eye
what is the difference between micro and macroadenomas (pituitary tumours)
macro larger than 10mm in diameter
are the majority of pituitary tumours malignant or benign
benign - arise from cell types in anterior lobe of pituitary gland
how do most pituitary tumours present
endocrine dysfunction
what is the treatment for prolactinomas
dopamine agonists- cabergoline
what is a high dose dexmethasone suppression test used to determine
adrenal or pituirary causes of cortisol excess
high dose will suppress pituitary causes only
what are thyroid hormones like in a thyrotropinoma (pituitary tumour)
TSH high, free T3 and free T4 high
what is used to shrink GH secreting pituitary tumours before surgery
pegvisomant and somatostatin analogues- octreotide
when is radiotherapy used for pituitary tumours
when too large to operate/ growing into cavernous sinus
what tests should you do if you suspect a pituitary tumour
early morning cortisol and prolactin
what are acoustic neuromas/ vestibular schwannomas
benign tumours derived from schwann cells
arise in cerebellopontine angle and affect the vestibular portion of cranial nerve 8
what should you suspect with bilateral accoustic neuromas in the young
NF 2
what is the pathology of vestibular schwannomas
Verocay bodies can be seen, which are palisading nuclei against a fibrillary background
what is the presentation of an acoustic neuroma
30-50 y/os
unilateral SNHL, tinnitus and vertigo
if big can have headache
facial pain/ numbness- if CN V involved
what is the management for vestibular schwannomas
serial observation- hearing aid, MRI, neuro exams
sterotatic radiosurgery
microsurgical excision
what are haemangioblastoma
benign, cystic, highly vascular tumours
develop in posterior fossa
what is the presentation of a haemangioblastoma
cerebral dysfunction (occur in post fossa) symptoms of raised ICP
associated with von hipple-landau syndrome - multiple haemangiomas which may be symptomatic (retinal angiomas, renal cell carcinoma and phaeochrmomcytoma)
what should GH levels be after oral glucose (100g)
less than 1mg/ml
what definitive test for acromegaly
IGF-1
what does the anterior intracranial circulation arise from
the internal carotids
what does the posterior intracranial circulation arise from
paired vertebral arteries- join to form basilar
what makes up the anterior circulation of the brain
internal carotid
ACA
MCA
anterior communcicating artery
where does the internal carotid arise from
common carotids at carotid bifurcation (C4)
what is the path of the internal carotid
enters the base of the skull through the carotid canal
transverses the foramen lacerum (does not pass through it)
what are the branches of the internal carotid
ophthalmic
anterior choroidal
posterior communicating
terminates into bifurcation into MCA and ACA
what is the path of the ACA
arches over corpus callosum in the longitudinal fissure
what does the ACA supply
medial part of left and right cerebral hemispheres, back to the parietal lobes
most of corpus callosum
anterior limb of internal capsule
part of caudate nucleus
is the MCA or ACA bigger
MCA
what is the path of the MCA
extends from the internal carotid to the sylvian fissure
exits fissure onto lateral surface of hemisphere
what does the MCA supply
majority of the lateral hemisphere, basal ganglia and internal capsule