ANTERIOR HORN CELL DISEASE (Motor Neuron Disease)

Question 1

Motor Neuron Disease

Disorders that cause degeneration of the motor neurons in the spinal cord (anterior horn cells) with/without similar lesions in the lower brainstem motor nuclei and/or the Betz cells of the brain and associated long tracts.

Characterized clinically by progressive wasting and weakness of the affected muscles without accompanying sensory, cerebellar, or mental changes

Answer 1

Amyotrophic Lateral Sclerosis (ALS)

more common in males

Mixed upper (spasticity, hyperreflexia, Babinski sign) and lowe r motor neuron (atrophy, fasciculations) signs

Pathophysiology

Degeneration of Betz cells, lower brainstem nuclei, descending corticospinal tracts, anterior horn cells

Clinical Presentation Highly Variable But Typically

Age at onset 20-60 years, most common after age of 50.

First sign often hand clumsiness or impaired dexterity with mild wasting/weakness of hand intrinsics.

Eventually, other hand/arm become involved.

Weakness/atrophy spreads proximally in arms.

Before long, legs become similarly affected.

Later, atrophic weakness spreads to tongue, pharynx, and muscles of respiration.

Accompanying symptoms include fasciculations, cramps, drooling, weight loss.

Question 2

Amyotrophic Lateral Sclerosis

Important “Rule of Thumb” Negatives

No sensory symptoms

Normal mentation

No extraocular muscle involvement

Bowel or bladder symptoms not prominent Decubiti rare

Fasciculations are rarely the presenting symptom

Answer 2

Progressive Bulbar Palsy

Dysarthria, dysphagia, dysphonia, chewing difficulty, drooling, respiratory difficulty usual features

Almost always progresses to generalized disease (i.e. ALS.).

Earlier the onset of bulbar symptoms in ALS, the shorter the course of the disease.

Question 3

(Progressive) Spinal Muscular Atrophy

M>F by 3.5:1

64 years.

Lower motor neuron deficits predominate due to degeneration of anterior horn cells

No upper motor neuron involvement.

Often begins with symmetric upper extremity involvement.

• Weakness, atrophy, respiratory difficulty

Answer 3

Primary Lateral Sclerosis

Age at onset usually 50 – 55 years.

Upper motor neuron (corticospinal) deficit prevail

Weakness, spasticity, hyperreflexia, Babinski signs.

Slow progression , but can evolve into ALS.

Question 4

Childhood Motor Neuron Disease

• Infantile Spinal Muscular Atrophy (Werdnig-Hoffman Disease)

– hypotonia, arreflexia, poor suck, breathing difficulty, death in 6 to 12 months

• Intermediate Spinal Muscular Atrophy (Chronic WerdnigHoffman Disease)
• Juvenile Spinal Muscular Atrophy (Kugelberg-Welander Disease) – milder than Werdnig-Hoffman