Neurology Flashcards
Stages of neural development
Dorsal induction Ventral induction Neuronal proliferation Neuronal migration Cortical organisation Myelination
Myelination on MRI
Pattern:
- Unmyelinated brain has more water than fat content –> relatively dark on T1 and brighter on T2 compared to cortex
- With myelination, this pattern reverses
- Spreads from central to peripheral, posterior to anterior
T1 precedes T2:
- T1 completed by 1 year
- T2 completed by 2 years
Subdural haematoma
Tearing of bridging VEINS (venous bleeding) –> bleeding into potential space
- Crescentic
- Cross sutures
- Follows dural folds
- Outlines subarachnoid space
- Most consistent finding with abusive head injury
Epidural haematoma
Arterial bleed secondary to skull fracture
- Lens-shaped bleeding from stripping of dura from the skull
- Bound by sutures
Subarachnoid haemorrhage
- Extends into sulci and fissures
2. Best seen on T2* or FLAIR MRI
Holoprosencephaly
Failure of embryonic forebrain to separate –> fusion of e.g. frontal lobes
*Abnormality of ventral induction i.e. separation
Lissencephaly
with agyria/pachygyria complex
Smooth brain with increased cortical thickness, cell-sparse layer
Agyria = absence of gyri; pachygyria = thickened cortex
DCX = more severe anteriorly; LIS1 = more severe posteriorly
*Abnormality of neuronal migration
Polymicrogyria
Lots of small gyri = appears nodular
- Can be focal or bilateral
- Overfolded cortex with false impression of cortical thickening
- Associated abnormal deep or elongated sulci
- Any disruptive process to cortex will be lined by polymicrogyria
Schizencephaly
Full-thickness cleft through hemisphere
- Often lined by polymicrogyria
- Open or closed lip
Causes:
- Intrauterine neuro insult (~20wk): CMV infection, HIE
- Genetic: COL4A1
Heterotopia
Abnormal position of grey matter
*Abnormality of neuronal migration
Focal cortical dysplasia
Subtle focal dysplastic cortex, can manifest as “blurring” of cortex (subtle finding)
*Accelerated myelination
EEG: normal background activity
- Alpha rhythm:
- 8-12Hz - usually gradually increases with age; infancy 6-8Hz, 3yrs >8Hz
- Prominent posteriorly on eye closure - Theta waves:
- 4-8Hz
- Normal in children up to 13yrs and in drowsiness/sleep - Delta waves:
- <4Hz
- Normal in deep sleep (stage 2 and 3)
- Focal finding: can be assoc with structural pathology
- Generalised finding: diffuse encephalopathy - Beta waves:
- >13Hz
- Often prominent in presence of drugs (barbituates, BZD)
- Commonly seen in frontal region
EEG: epileptiform discharges
- Sharply contoured discharges
- Sharp waves <200ms
- Spikes <70ms
- No difference in biological significance between 2 forms - Multiple phases
- Clearly disrupts background activity
- After-coming slow wave
- Sensible electrical field distribution
Genes associated with Charcot-Marie-Tooth Disease Type 1
Autosomal dominant inheritance: CMT1A - PMP22 (17p11) CMT1B - Po (1q22) CMT1C - LITAF (16p13) CMT1D - EGR2 (10q21)
Genes associated with Charcot-Marie-Tooth Disease Type 2 and Type 3
CMT2 - MFN2 (autosomal dominant)
CMT3 - PMP22 (point mutations) - 8q23, 17p11, 10q21
Risk factors for CP
Male
Prematurity - 43% of pts with CP are prem
Low birth weight - 43%
Multiple birth (twins/triplets) - 11%
Birth asphyxia/adverse intrapartum events - 10%
Infection in late pregnancy - sig. RF for term neonates
Previous/multiple MCs - ?genetic, clotting disorders
APGAR score at 1min
Breech position
Maternal smoking, illicit substance use
Genetic component
Strongest predictor of mortality in CP
Profound intellectual disability
- 22% die by 5yrs
- 50% die by 18yrs
GMFCS Level 1
- Can walk independently on all surfaces
- Can run and jump, but speed, co-ordination and balance are reduced
- 35% of CPs
GMFCS Level 2
Walks independently, but:
- Difficulty walking on uneven surfaces, inclines, crowded places
- 24% of CPs
GMFCS Level 3
- Requires assistive mobility devices, orthoses for walking
- Wheelchair required for long distances
- Sits independently, has independent floor mobility
- 12% of CPs
GMFCS Level 4
- Uses power mobility outdoors and in community
- Supported sitting function
- Requires assistance with standing transfers
- Mobility is limited
- 13% of CPs
GMFCS Level 5
- No independent mobility
- Poor antigravity head and trunk postures
- Require tilt in space and seating systems
- 15% of CPs
Selective dorsal rhizotomy
Laminectomy L1-S1 –> dorsal nerve root transection
- 20-30% sensory nerve rootlets from L2-S1
To reduce lower limb spasticity
Irreversible
Indications for selective dorsal rhizotomy
Spastic diplegia: GMFCS II to III
Moderate to severe spasticity
Limited contractures
Motivated patients and parents: intense functional training over 1-2yrs follows
Goal: gait kinematics improvement, spasticity management
- No supporting evidence that it improves function (i.e. general activities) and participation
*Does NOT prevent further need for orthopaedic surgery
Intrathecal baclofen
Indication: severe, generalised spasticity that has failed conservative treatment (including botox)
MOA: GABA agonist - delivered directly around spinal cord, decreases neurotransmission of afferent nerve fibres.
Advantage of IT baclofen c.f. PO
Delivered directly around spinal cord, overcomes side effects secondary to large oral doses
- 1/100th of oral dose
- Small amount crosses BBB
Side effects and withdrawal effects of IT baclofen
Overdosing:
- Sedation
- Light-headedness
- Respiratory depression
- Seizures
- LOC/Coma
Withdrawl: life-threatening
- Hyperthermia
- Rhabdomyolysis
- Seizures, coma
- Multiple organ system failure
Indications for Botulinum Toxin A
Indications:
- Spasticity and dystonia - specific muscle groups
- Interferes with function or cares
- Severe drooling - can inject into salivary glands
Aim: delay surgery
Side effects of BTA
Fibrosis
LRTI/URTI in those with pre-existing dysphagia and GMFCS V
Indication for deep brain stimulation in CP
Dyskinetic CP with dystonia and choreoathetosis
- Generalised condition
- Timing of implantation: earlier the better
MOA: disruption of electrical signals of extrapyramidal pathway
Effects: improvement noted subjectively but not on formal assessment
CP Prevention
- Magnesium sulfate: antenatal IV MgSO4 for mothers in premature labour with birth imminent before 32 weeks has shown significant reduction in risk of CP at 2yrs of age
- Cooling term infants with HIE to 33.3 degrees for 3 days starting within 6hrs of birth reduces risk of dyskinetic or spastic quadriplegic forms of CP
Causes of hemiplegic CP
- Injury to white matter in utero 34%
- Focal lesions that may have resulted from stroke 27%
- Infections (e.g. CMV)
- Cortical malformation: lissencephaly, polymicrogyria, schizencephaly, cortical dysplasia
- Focal cerebral infarction secondary to intrauterine or perinatal thromboembolism related to thrombophilic disorders e.g. anticardiolipin Abs
Clinical criteria for neurofibromatosis type 1:
2 or more of…
- 6 or more cafe-au-lait spots
- -> >5mm in prepubertal
- -> >15mm in pubertal
- 2 or more neurofibromas or 1 plexiform neurofibroma
- 2 or more Lisch nodules
- Inguinal/axillary freckling
- Optic glioma
- Distinctive osseous lesions (e.g. sphenoid bone dysplasia)
- 1st degree relative with NF
Features of NF1 more common in <5yo
- CAL (present at birth - increase in size, # and pigmentation)
- Plexiform neurofibromas (present from birth)
- Optic gliomas
- Freckling
- UBOs (increase in # until 10yo, then start disappearing)
Genetics of NF1
Autosomal dominant, but 30-50% are sporadic
Ch17q11.2
Mutation of NF1 gene - loss of function mutation of tumour suppressor gene
- Protein = neurofibromin - regulates cell signal transduction pathways, inhibitor of Ras (oncogene)
Clinical criteria for neurofibromatosis type 2:
1 of…
- Bilateral vestibular schwannomas
- First degree relative with NF2 AND
- Unilateral schwanomma OR
- 2 or more of: meningioma, schwannoma, glioma, neurofibroma or posterior subcapsular lens opacity - Multiple meningiomas (2 or more) AND
- Unilateral schwannoma OR
- 2 or more of: meningioma, schwannoma, glioma, neurofibroma or posterior subcapsular lens opacity
Genetics of NF2
Autosomal dominant, 50% are sporadic NF2 gene on ch 22q1.11 Tumour suppressor gene: merlin Merlin links between membrane proteins and cell cytoskeleton Phenotype depends on type of mutation: - Frameshift/nonsense: severe disease - Missense: milder disease
Management and prognosis of NF2
Mx:
- Annual MRI scans
- Early surgical treatment of schwannomas, aim = preserve hearing
- Regular ophthal review and monitor vision
- Avastin (bevacizumab) - shrinks vestibular schwannomas
Prognosis:
- Average age of death = 36yrs
- Average time from first Sx to death = 15yrs
- Major cause of morbidity = spinal tumours, vestibular schwannomas (pain, tinnitus, hearing loss)
Diagnostic criteria for tuberous sclerosis:
- 2 major criteria or 1 major and 2 minor criteria
Major criteria:
- Skin/eye: >3 hypomelanotic macules, shagreen patch, forehead plaques OR facial angiofibromata, peri(ungal) fibromas, multiple nodular retinal hamartomas
- CNS: subependymal nodules, cortical tubers, subependymal giant cell astrocytoma
- Others: renal angiomyolipoma, cardiac rhabdomyoma, lymphangioleiomyomatosis (LAM)
Minor criteria:
- Skin/eye: confetti skin lesions, dental enamel pits, intra-oral fibromas, retinal achromic patch
- CNS: cerebral white matter migration lines
- Other: non-renal hamartomas, multiple renal cysts, bone cysts, rectal polyps
Respiratory manifestations of tuberous sclerosis
LAM - lymphangioleioangiomyomatosis
- Proliferation interstitium and dilated lymphatics –> obstruction and subsequent cystic lung changes
- Presents with PTX and dyspnoea
- F»M, poor prognosis
CNS manifestations of tuberous sclerosis
85% of TS have CNS Cx!!!
- Seizures (most significant cause of morbidity - 75%)
- Infantile spasms (20%) - hard to treat
- Myoclonic, focal, GTCS
- Can be refractory to treatment - Intellectual disability (50%)
- 30% are profound - Behavioural issues
- ADHD, autism, sleeping problems, aggression, psychiatric disorders - CNS changes/tumours (>75%)
- Subependymal nodules, giant cell astrocytoma (teens), cortical tubers, white matter radial migration
- Obstructive hydrocephalus
mTOR inhibitors for tuberous sclerosis
- Sirolimus: reduction in size of angiomyolipomas, improved PFTs for LAM pts
- Everolimus: reduced seizure #, reduced subependymal giant cell astrocytomas
- Topical rapamycin: reduce size of facial angiofibromas
Genetics of tuberous sclerosis
Autosomal dominant, 2/3 - sporadic
- TSC1 gene (9q34): hamartin
- TSC2 gene (16p13.3): tuberin
- %proband with TS and confirmed mutation: TSC2 in 69%
- Simplex cases with TS: 60-70%
- If parents of confirmed TS pt is normal, recurrence risk is 2% (due to gonadal mosaicism)
Anencephaly
Incidence is 1 in 10000 live births (underestimated due to terminations/stillbirth)
Failure of closure of anterior neural tube
Absence of bilateral hemispheres and hypothalamus
- Absence of pituitary gland –> abnormal development of end-organs and associated Cx e.g. adrenal insufficiency
- Antenatal Ix: USS, maternal serum alpha-fetoprotein
Dandy-Walker Malformation
Continuum of posterior fossa anomalies:
- Cystic dilatation of 4th ventricle
- Hypoplasia of cerebellar vermis
- Enlarged posterior fossa with elevation of lateral venous sinuses and tentorium
- Hydrocephalus
DDx for acute hemiplegia
- Transient postictal hemiparesis (Todd’s paralysis): post-ictal phenomenon, usually lasts for 24-48hrs, EEG activity consistent with sz or post-ictal status. Secondary to neuronal exhaustion. MRI shows no acute infarct
- Complex migraine: usually assoc. with a significant headache with focal deficits lasting hours, positive FHx!, MRI shows no acute infarct
- Alternating hemiplegia of childhood: progressive neurological disorder presenting <2yrs, with distinct episodes of hemiplegia lasting minutes to hours where weakness alternates between sides. Seizures are common, but not during periods of weakness. Unknown aetiology.
AEDs:
Greatest risk of Stevens-Johnson Syndrome
Lamotrigine: 1/100
Others: CBZ, PHT, OXC - 1-6/10000
Avoid by starting low and going slow
Which AED is associated with SJS in Han Chinese population?
Carbemazepine
CBZ-SJS strongly associated with HLA-B*1502: Han Chinese, Hong Kong Chinese, Thai
Foetal valproate syndrome
Craniofacial abnormalities, radius/limbs abnormalities, CHD, genitourinary abnormalities (e.g. hypospadias), developmental delay, increased risk of autism
VPA associated with higher risk of teratogenicity and it is dose-dependent (>800mg) - if unavoidable, recommend <330mg daily in combination with LTG
Which AED is associated with the development of neural tube defects?
VPA 1-5%
CBZ 0.5-1%
AEDs:
The greatest risk factor for teratogenicity/malformations…
Polytherapy, high drug levels in 1st trimester
Teratogenic effects of topiramate
CHDs, orofacial clefts, hypospadias
Major cognitive side effects of AEDs
All AEDs can cause fatigue, impaired cognition - compounded by polytherapy
Suicidality risk reported as increased with all AEDs
PHB: long-term cognitive effects even after cessation of drug
LVT: psychosis, suicidality, homicidality
VBG: psychosis, depression
Inducers of CYP450 system
PHT, PHB, CBZ
AEDs that are renally excreted
GBP, VGB, TPM, LVT, ZNS
AEDs that undergo hepatic clearance
PHT, PHB (75%), CBZ, OXC, VPA, LTG, BZ (diazepam)
Phenytoin: MOA, Adv, Disadv, SE
- MOA: Na channel blocker > Ca channel blocker
- Adv: widely available, broad spectrum
- Disad: zero order kinetics, drug interactions
- SE: rash, SJS, serum sickness, hirsutism, gum hypertrophy, osteoporosis, headache, nausea, dizziness, somnolence/fatigue, ataxia, macro anaemia (decr. folate absorption)
Carbamazepine: MOA, Ind, Adv, Disadv, SE
- Dose: 5mg/kg/day –> 15-20mg/kg/day
- MOA: Na channel blocker
- Ind: focal sz and GTCs (+/- secondary generalisation)
- Adv: well tolerated, can be used for monotherapy or adjunctive, can be used for both focal and generalised epilepsies
- Disadv: interactions (decr OCP, warfarin) and autoinduction - lowers other AED levels, produces toxic metabolite - epoxide, worsens absence and myoclonus
- SE: rash, SJS (rare), transient leucopenia (10-20%), aplastic anaemia 1/200000, headache, nausea, dizziness, somn/fatigue, ataxia, hyponatremia, hepatotoxicity
Valproate: MOA, Ind, Adv, Disadv, SE
- Dose: 10mg/kg/day –> 20-30mg/kg/day
- MOA: Na channel blocker > Ca channel blocker, GABAergic action
- Ind: focal, GTC, absence sz, myoclonic, tonic
- Adv: broad spectrum (esp effective for generalised), well tolerated, can be given via multiple routes
- Disadv: teratogenicity! Interactions with other AEDs - raises other AED levels as it is a CYP enzyme inhibitor
- SE: weight gain, alopecia, essential tremour, thrombocytopenia/platelet dysfxn, hepatic failure (1/37000 –> esp <2yo, mental retardation and polytherapy), pancreatitis, thyroid dysfxn, other SE assoc. w/ Na channel blockers (headache, nausea etc)
Ethosuximide: MOA, Ind, Adv, Disadv, SE
- MOA: T-type Ca channel blocker
- Ind: CAE and JAE only - thalamo-cortical circuit in 3Hz spike and wave
- Adv: rapid, complete absorption, titrate to response
- Disadv: ineffective for GTC
- SE: rash –> SJS, GI Sx - nausea (33% at onset, requires slow titration), blood dyscrasias