CNS Flashcards
A lady with albinism finds it difficult to go outside due to finding the sunlight too bright. In which structure is she lacking melanin? Why is this difficult for her?
Retinal pigmented epithelium
Albinism causes loss of pigmentation
Melanin in the retinal pigment epithelium prevents reflections within the eyeball
Loss of melanin in the RPE will cause reflections and everything will appear bright in bright light
pt presents with right sided hemianaesthesia. Which lobe has most likely been affected to cause this finding?
Left parietal lobe
Name one disorder that causes excessive movement
Huntingtons disease, stroke in subthalamic nucleus,
cerebellar lesion, Sydenham’s chorea
Name one condition other than Parkinson’s disease that causes paucity of movement
Stroke of motor cortex, myasthenia gravis, motor
neurone disease, coma, brainstem herniation
A stroke affected a pts posterior cerebral artery. Which other artery is involved to ensure that macular vision is preserved?
MCA (middle cerebral artery)
technique to increase chance of eliciting tendon reflexes?
Jendrassik manouevre (clench teeth, interlock fingers and pull arms apart)
Why do you get macular sparing after a stroke?
⇒ Stroke can affect the posterior cerebral artery
⇒ Most of occipital lobe will be lost
⇒ Middle cerebral artery supplies the occipital pole (represents the macula)
⇒ Macular function (central vision) will be spared
How does the facial motor nucleus function?
- The part of the facial motor nucleus that supplies the upper half of the face receives UMNs from both hemispheres
- The part of the facial motor nucleus that supplies the lower face only receives a contralateral UMN input
How do UMN lesions involving the face and facial nerve palsies differ?
- UMN lesions involving the face will spare the forehead
- True facial nerve palsies will affect all of the muscles of facial expression
Differentiate between meningocoele, meningomylocoele and myeolocoele
Menigocoele = open bubble of just CSF, no spinal cord involvement
Meningomyelocoele- CSF AND spinal cord involved- Cystic lesion protrudes out through defect in the dorsal arches
Myeolocoele= spinal cord completely open due to incomplete vertebral arch
- Rachischisis
What does the presence of xanthocromia in CSF suggest?
SAH occurred over 12 hours ago
PCA aneurysms can compress which cranial nerve?
Oculomotor - it runs parallel to the PCA
Damage where causes inferior quadrantanopias?
Damage to the superior optic radiations which run in the parietal lobe
Damage where causes superior quadrantanopias?
Damage to the inferior optic radiations in the temporal lobe
Where would you find a lesion that causes a contralateral homonymous hemianopia with macular sparing?
The PCA in the occipital lobe
What is the other name for the inferior optic radiations?
Meyer’s loop
Other name for absence seizures?
Petit mal
Symptoms of temporal lobe seizures?
Olfactory hallucinations and deja vu
Commonest cause of excessive daytime sleepiness?
Sleep apnoea - narcolepsy is rare!!
What is amaurosis fugax? What artery is most commonly involved?
Transient blindness due to hypoxia of the retina caused by blockage of the central retinal artery
What structure does the superior cerebellar artery supply in addition to the cerebellum?
Midbrain
Thalamoperforator arteries are branches of which main artery?
Posterior cerebral
Where do the lenticulostriate arteries take their origin?
Middle cerebral artery - they branch off of the MCA to supply the basal ganglia and internal capsule
The cuneate fasciculus contains fibres from which body region?
C1-T6
The gracile fasciculus contains information from the LOWER part of the body
The raphe nuclei in the brainstem produce which neurotransmitter?
5HT- serotonin
Where is noradrenaline produced?
The locus coreuleus
What is the consequence of blockage of the arachnoid granulations e.g. in SAH?
CSF accumulates and causes raised ICP ( CSF usually drains through granulations
Define tract, fasciculus and funinculus
Tract - distinct white matter pathway running between two regions that contains axons travelling in ONE DIRECTION ONLY
Fasciculus - a subdivision of a tract
A funinculus - kinda funny because it contains axons travelling IN TWO DIFFERENT DIRECTIONS
What can you not use long term for anxiety tx?
Benzos- addictive, severe side effects, can be used in suicide attempts
Tx for anxiety?
- SSRIs (mainstay) / pregabalin (GABA analogue)
- Cognitive behavioural therapy
Describe the epidemiology of OCD
Young people, 75% experience symptoms before 30, M:F 1:1, 2% of the population
What structure is commonly enlarged in schizophrenia?
Ventricles
Describe distribution of D2 receptors in the brain
Rich in striatum and midbrain, lower in cortex
Which dopamine pathway is overactive in schizophrenia?
The mesolimbic - all “limbered up” ready to cause schizophrenia
Mesocortical is underactive
Tuberoinfundibular has an endicronological role
Who coined the word schizophrenia?
Eugen Bleuler
How do you differentiate between different schizophrenia subtypes ?
Simple - self absorbed and socially withdrawn, no hallucinations/ delusions
Paranoid - profound hallucinations/delusions
Heberphrenic- inappropriate affect, disjointed behaviour and thought disorder ( also caused disorganised schizophrenia)
List the first rank symptoms of schizophrenia
- Auditory hallucinations
- Somatic hallucinations
- Passivity experiences
- Thought withdrawal, broadcast or insertion
- Delusional perceptions
The posterior limb of the internal capsule represents which part of the body?
Trunk and lower limbs
Which part of the internal capsule represents the face?
The genu
What nerve palsy is caused by herniation of the uncus?
CN 3
Which midbrain structure is important for motor control?
The red nucleus
Why might a stroke affecting the lateral motor cortex compromise swallowing?
Denervation of the cranial nerve nuclei which distribute LMNs in the vagus nerve
Where are pattern generator neurones found?
In the medulla
What does the medial lemniscus contain?
Decussating second order sensory fibres in the DCML
What does the medial longitudinal fasciculus do? What can damage here cause?
integrates movement of the eyes by linking the 3 CNs involved in eye movements
internuclear ophthalmoplegia - an ocular movement disorder that presents as an inability to perform conjugate lateral gaze
Which part of the brainstem lies at the level of tentorium cerebelli?
The midbrain
What white matter structures in the midbrain connect the cerebral hemispheres to the brainstem?
Crus cerebri
What are the superior colliculi?
Features of the dorsal midbrain that deal with reflex actions to visual stimuli
Which cranial nerve emerges ventrally from the ponto-medullary junction?
Abducens nerve
Facial nerve emerges laterally
CNS shares and embryological origin with which tissue?
Skin - ectoderm
Gut derives from endoderm and muscle from mesoderm
Potential cause of rapid onset dementia in young people?
Prion disease or an aggressive brain tumour
Describe GCS scoring
Eye Opening Response • Spontaneous 4 points • To verbal stimuli 3 points • To pain only 2 points • No response 1 point
Verbal Response • Oriented 5 points • Confused conversation, but able to answer qs 4 points • Inappropriate words 3 points • Incomprehensible speech 2 points • No response 1 point
Motor Response
• Obeys commands 6 points
• Purposeful movement to painful stimulus 5 points
• Withdraws in response to pain 4 points
• Flexion in response to pain (decorticate posturing) 3 points
• Extension response in response to pain (decerebrate posturing) 2 points
• No response 1 point
Pt is able to point to an object when asked and can articulate well but not repeat the objects name - site of lesion?
Arcuate fasciculus
Site of lesion in hemispatial neglect?
R parietal lobe
How do plaques form?
Amyloid precursor protein repairs neurones following damage and is broken down by alpha and gamma secretase
If Beta secretase gets involved, the resulting parts of APP are no longer soluble and accumulate between neurones, reducing signal transmission
How do tangles form?
Tau proteins play a role in stabilising microtubules within the neuronal cytoskeleton
• Microtubules help to mobilise nutrients around the neuron
• Beta amyloid plaques (outside the neuron) induce pathological processes within the neuron
• Results in hyperphosphorylation of Tau proteins
• Causes a change in the shape of Tau proteins
What are the three components of the general adaptation syndrome?
Alarm, resistance, exhaustion
Outcomes of proximal MCA occlusion? Specifically if left/right sided?
Contralateral hemiparesis
Contralateral sensory deficit (often solely face and arms)
Contralateral homonymous hemianopia
If left sided:
Aphasia
More commonly right sided:
Contralateral (i.e. left sided) hemispatial neglect
Outcomes of PCA occlusion?
Contralateral homonymous hemianopia with macular sparing
Contralateral sensory loss (due to thalamic involvement)
What is needed to classify as a TACs stroke?
All 3 of:
- Unilateral weakness (+/- sensory deficit) of the face, arm and leg
- Homonymous hemianopia
- Higher cerebral dysfunction
• Dysphasia / aphasia
• Visuospatial disorder
What is needed to classify as a PACs stroke?
Only 2 of:
- Unilateral weakness (+/- sensory deficit) of the face, arm and leg
- Homonymous hemianopia
- Higher cerebral dysfunction
• Dysphasia / aphasia
• Visuospatial disorder
What is needed to classify as a POCs stroke?
One of the following:
- Cranial nerve palsy and contralateral motor/sensory deficit
- Bilateral motor/sensory deficit
- Conjugate eye movement disorder
- Cerebellar dysfunction
- Isolated homonymous hemianopia (with macular sparing)
What is needed to classify as a LACs stroke?
Pure sensory deficit
Pure motor deficit
Sensory-motor deficit
Ataxic hemiparesis
