Neurology Flashcards
(44 cards)
What causes Lambert-Eaton myasthenia syndrome?
Small cell lung cancer - antibodies target and damage voltage-gated calcium channels in the presynaptic terminals of the neuromuscular junction. Less acetylcholine is released
What are the symptoms of Lambert-Eaton myasthenia syndrome?
Slow development of proximal muscle weakness. Can also affect eyes, speech and swallow, autonomic.
Reduced reflexes - with post-titanic potentiation
What is the treatment for Lambert-Eaton syndrome?
Investigate for small-cell lung cancer
Amifampridine - allows more acetylcholine to be released in the neuromuscular junction synapses
Also: immunosuppression or IVIG
What is the genetics for Huntington’s?
Autosomal dominant trinucleotide repeat disorder of CAG in huntingtin gene on chromosome 4
Anticipation is a feature of what type of genetic disorder?
Trinucleotide repeat disorders - successive generations have more repeats in the gene
What medications are used in Huntington’s to suppress the disordered movement?
Antipsychotics
Benzodiazepines
Dopamine-depleting agents
What is Charcot-Marie-Tooth Disease?
Genetic - usually autosomal dominant
Affects peripheral motor and sensory nerves
What are classical features of CMT?
High foot arches (pes caves)
Distal muscle wasting causing “inverted champagne bottle legs”
Weakness in the lower legs, particularly loss of ankle dorsiflexion
Weakness in the hands
Reduced tendon reflexes
Reduced muscle tone
Peripheral sensory loss
What is the ABCDE of causes of peripheral neuropathy?
A - alcohol
B - B12 deficiency
C - Cancer and CKD
D - Diabetes and Drugs (e.g. isoniazid, amiodarone and cisplatin
E - every vasculitis
What is tuberous sclerosis?
Genetic
Hamartomas (benign neoplastic growths of tissue) usually in skin brain, lungs, heart, kidneys, eyes
What mutations in genes causes tuberous sclerosis?
TSC1 gene on chromosome 9 (codes for Hamartin)
TSC2 gene on chromosome 16 (tuberin)
Hamartin and tuberin interact with each other to control the size and growth of cells
What are the skin signs of tuberous sclerosis?
Ash leaf spots (depigmented)
Shagreen patches (pigmented)
Angiofibromas on nose and cheeks
Sublingual fibromata (nail bed)
Cafe-au-lait spots
Poliosis - isolated patch of white hair on the head, eyebrows, eyelashes or beard
Often present with epilepsy and skin changes
What causes seizures?
Either too little inhibition of neuronal activity (too little GABA) or too much excitation (too much glutamate)
What receptors does glutamate bind to in the synaptic cleft?
AMPA which causes Na+ entry
NMDA which causes Ca2+ entry
Propagates the signal
How does GABA inhibit signal propagation?
It binds to GABA-A receptors on the excitatory neurons causing Cl- to enter
How is GABA removed from the synaptic cleft?
GABA transporter 1
It is then degraded by the enzyme gamma-aminobutyric acid aminotransferase (GABA-T)
Which antiepileptics block calcium channels as well as sodium channels?
Lamotrigine
Zonisamide
Topiramate
Valproic acid
How do Gabapentin and Pregabalin work?
High voltage calcium channel blockers
How does levetiracetam work?
Binds to SV2A on walls of glutamate vesicles impairing its release
How do benzodiazepines and barbiturates work?
Bind to GABA-A receptor prolonging the opening of channel, increasing Cl- influx
How does Tiagabine work?
Selective inhibitor of GAT1, blocking FGABA reuptake
How does Vigabatrine work?
Irreversibly inhibits GABA-T, preventing catabolism of GABA, increasing levels of GABA in the brain
Which antiepileptics can cause hyponatraemia?
Carbemazepine and oxycarbemazepine
What antiepileptic can cause visual field loss?
Vigabatrin
