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  • The doctor of the future will give no medicine but will interest his patients in the care of the human frame, in diet and in the cause and prevention of disease. ~Thomas Edison

Central Nervous System I MCQs

Posted by Dr KAMAL DEEP on June 4, 2012

Action potentials normally are generated by the opening of sodium channels and the inward movement of sodium ions down the intracellular concentration gradient. Depolarization of the neuronal membrane opens potassium channels, resulting in outward movement of potassium ions, repolarization, closure of the sodium channel, and hyperpolarization. Sodium or potassium channel subunit genes have long been considered candidate disease genes in inherited epilepsy syndromes, and recently such mutations were identified. These mutations appear to alter the normal gating function of these channels, increasing the inherent excitability of neuronal membranes in regions where the abnormal channels are expressed.

All of the following are neurologic channelopathies
except – (AI 05)
a) Hypokalemic periodic paralysis
b) Episodic ataxia type 1
c) Familial hemiplegic migraine
d) Spinocerebellar ataxia 1

Ans is ‘d’ i.e., Sphinocerebellar Ataxia -1 [Ref Harrison 16 1"/e p. 2339 & 15'h/e p. 2321]

All of the following are calcium channelopathies,
except – (AIIMS May 05)
a) Episodic ataxia -1
b) Spinocerebellar ataxia-6
c) Familial hemiplegic migraine
d) Hypokalemic periodic paralysis

Episode weakness is due to – (PG1 87)
a) Hypokalaemia b) Dermatomyositis
c) Paramyotonia congenita d) Myasthenia gravis
e) Hypophosphatemia

Cataract is associated with PGI 88
a) Pseudo muscular hypertrophy b) myotonia congenita c) myotonic dystrophy d) SLE

In a patient, muscle cramps on exercise, +ve
myoglobulinemia, the disorder is – (PGI 98)
a) Pompe’s disease b) Myotonia congenita
c) Myotonic dystrophy d) Mc ardle’s disease

Table 366-1 Examples of Neurologic Channelopathies


Category Disorder Channel Type Mutated Gene Chap. Ref.
Genetic
Ataxias

Episodicataxia-1

Episodicataxia-2

Spinocerebellar ataxia-6

K

Ca

Ca

KCNA1

CACNL1A

CACNL1A

373
Migraine

Familial hemiplegic migraine 1

Familial hemiplegic migraine 3

Ca

Na

CACNL1A

SCN1A

14
Epilepsy

Benign neonatal familial convulsions

Generalized epilepsy with febrile convulsions plus

K

Na

KCNQ2, KCNQ3 SCN1B 369
Periodic paralysis

Hyperkalemic periodic paralysis

Hypokalemic periodic paralysis

Na

Ca

SCN4A

CACNL1A3

387
Myotonia

Myotonia congenita

Paramyotonia congenita

Cl

Na

CLCN1

SCN4A

387
Deafness Jervell and Lange-Nielsen syndrome (deafness, prolonged QT interval, and arrhythmia) K KCNQ1, KCNE1 30
  Autosomal dominant progressive deafness K KCNQ4  
Autoimmune
Paraneoplastic

Limbic encephalitis

Acquired neuromyotonia

Cerebellar ataxia

Lambert-Eaton syndrome

Kv1

Kv1

Ca (P/Q type)

Ca (P/Q type)

101

101

101

101

 

Whereas the specific clinical manifestations of channelopathies are quite variable, one common feature is that manifestations tend to be intermittent or paroxysmal, as occurs in epilepsy, migraine, ataxia, myotonia, or periodic paralysis. Exceptions are clinically progressive channel disorders such as autosomal dominant hearing impairment.

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