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Flashcards in Motor Neuron Diseases Deck (19)
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Neuromuscular diseases affect motor units which are made up of

motor neurons, their motor axons, and secondarily the motor fibers they innervate


Spinal muscular atrophy presents at 3 stages, they are:

- infantile (Werdnig Hoffman)
- juvenile (Wohlfart- Kugleberg Welander)
- adult (Adult spinal muscular atrophy)


The infantile and juvenile forms of Spinal muscular atrophy follow which inheritance pattern

Autosomal Recessive


Adult Spinal muscular atrophy inheritance patttern?

sporadic and occasionaly familial


Features of infantile SMA

- Auto recessive
- Hypotonicity
- Hyporeflexia
- Fatal
- Tongue fasiculations
- Poor Suck Reflex
- Abdominal Respirations


Babies with SMA (Werdnig- Hoffman) generally die young due to what?

Respiratory failure


EMG of SMA (WH) will show what

Denervation and fasciculations


Muscle biopsy of someone with SMA will show?

group fiber atrophy


Mutation in infantile SMA?

survival motor neuron gene on chromosome 5Q


Differentiating spinal muscle atrophy from myopathies

EMG and biopsy show denerveation and serum CK is generally normal


Mutation in juvenile SMA

survival motor neuron gene on chromosome 5


The survival motor neuron gene has two copies, SMN1 and SMN2. SMN1 is absent in spinal muscular atrophy and they size of SMN2 determines if the patient has the neonatal or juvenile form (larger in the juvenile form)



Juvenile SMA called

Wohlfart Kugleberg Wolander


Progressive Bulbar Palsy

A presentation of ALS which primarily affects muscles innervated by the medulla neurons, causing tongue and palate weakness.



Manifests with upper and lower motor neuron symptoms and findings as well as "bulbar" weakness.


Progressive lateral sclerosis

affects primarily the upper motor neurons with little atrophy or signs of denervation


Some other things to consider when diagnosing ALS

- Multisystem atrophy: late onset degenerative disease that could affect lower motor neurons, autonomic neurons and cerebellar neurons

- Hereditary cerebellar degeneration: can't swallow plus ataxia

- Tumors of the craniocervical junction

- Cervical canal disease or cervical spondylosis: Deg disc dz. Arm hand atrophy or weakness, spasticity from compression of the pyramidal tracts.

- post polio syndrome: patients with a history of polio in childhood may later develop progressive lower motor neuron disease. The cause is unclear.

- Polyglucosan body disease: glycogen storage disorder that presents in younger individuals with a lower motor neuron type weakness

- Hyperparathyroidism: elevated serum calcium and parathyroid hormone level are diagnostic

- Kennedy disease: a more benign disorder that may present without a family history...gynecomastia and testicular atrophy


Gross pathology of ALS

lack of myelin and loss of anterior horn neurons


Microscopic pathology

Eosinophilic inclusion bodies in anterior horn cells. This same change would be expected in the motor nuclei of the brainstem.