Motor Neuron Disorders

Question 1

What is a motor neuron disease?

Answer 1

Degeneration of the motor neurons (anterior horn cells) in the spinal cord

Clinically presents by progressive wasting and weakness of affected muscles

NO sensory, cerebellar, or mental changes

Question 2

What acquired motor neuron dx is associated w/ asthma?

Answer 2

Hopkins Syndrome

Question 3

What are the motor neuron diseases?

Answer 3

Amyotrophic Lateral Sclerosis (ALS)
Progressive Bulbar Palsy (PBP)
Spinal Muscular Atrophy (SMA)
Primary Lateral Sclerosis (PLS)
Atypical ALS (w/ frontotemporal dementia)

Question 4

What is Amyotrophic Lateral Sclerosis also referred to as?

Answer 4

Lou Gehrig’s Dx

Question 5

What do the parts of Amyotrophic Lateral Sclerosis mean? (Break it down)

Answer 5

A = without
Myo = muscle
Trophic = nourishment
Lateral = side of the spinal cord
Sclerosis = hardening/scaring

Question 6

Are there any definite risk factors for ALS?

Answer 6

No, but some theories are developing

Question 7

How prevalent is ALS worldwide?

Answer 7

5/100,000

1/20,000

Question 8

Amyotrophic Lateral Sclerosis is associated w/ mixed U and L motor neuron signs. What are they?

Answer 8

Upper (spasticity, hyperreflexia, Babinski sign)

Lower (atrophy, fasciculations)

Question 9

What’s the patho-phys of ALS? Age distribution?

Answer 9

Degeneration of anterior horn cells and lateral and ventral corticospinal tracts

• pyramidal Betz cells
• brainstem motor nuclei of the lower cranial nn
• corticospinal/corticobulbar tracts

Etiology unknown
- familial in 5% of cases

Ages 20-60

Question 10

What’s the clinical presentation of ALS?

Answer 10

Gait disorder
Limb weakness
Speech or swallowing difficulty

Wt loss d/t loss of muscle bulk (50+ lbs)
Cramps
Fasciculations,
Tongue atrophy

Question 11

What are some of the lab results that contribute to an ALS dg?

Answer 11

EMG: widespread denervation and reinervation

CPK (serum creatinine): normal to slightly inc

CSF: normal

Imaging studies: normal

Muscle biopsy: not req

Question 12

Important diagnostic negatives of ALS include:

Answer 12

No sensory sxs

Normal mentation
- Steven Hawking still kicks ass at science

No extra-ocular m involvement

Bowel Bladder sxs not prominent

Decubiti rare
- pressure ulcer

Question 13

What’s the prognosis of ALS?

Answer 13

Poor

Relentlessly progresive (LE = 2-5 years)

No remissions, relapses, or stable plateaus

Death d/t: resp failure, pneumonia (aspirations), pulmonary embolus (d/t immobility)

Question 14

What’s a tx option in ALS?

Answer 14

Riluzol (Rilutek), glutamate inh

• 3-6 months LE extension
• expensive

Question 15

What’s the presenting sx in 20% of MND?

Answer 15

Progressive Bulbar Palsy

Question 16

How does Progressive Bulbar Palsy present?

Answer 16

Involvement of motor nuclei in lower cranial nn

Dysarthria, dysphagia, chewing and resp difficulty

Question 17

Does Progressive Bulbar Pasly progress to ALS?

Answer 17

Yes, often

Question 18

How many pts presenting with MND have Progressive Spinal Muscular Atrophy (SMA)?

Answer 18

10%

Question 19

Are males or females more affected by SMA? What’s the age of onset?

Answer 19

Males

64

Question 20

What deficits occur in Spinal Muscle Atrophy? Will it progress to ALS?

Answer 20

Lower motor neuron
- weakness, atrophy, resp difficulty, fasciculations

NO upper motor neuron

Can (rarely)
- Better survival rate vs ALS

Question 21

What’s the focal difference between Spinal Muscular Atrophy and Primary Lateral Sclerosis?

Answer 21

SMA = lower motor neuron involvement

PLS = upper motor neuron involvement

Question 22

What are the attributes of Primary Lateral Sclerosis?

Answer 22

In 2-4% of pts that present w/ MND

Onset 50-55 yo

UMN (weakness, spasticity, hyperreflexia, Babinski +

Can evolve to ALS
- better survival rate

Question 23

An infant presents w/ hypotonia, arreflexia, poor suck and difficulty breathing. Diagnosis? Prognosis

Answer 23

Infantile Spinal Muscular Atrophy

Poor, death in 6-12 months

Question 24

When does Juvenile Spinal Muscular Atrophy present?

Answer 24

Adolescence