Disorders of Motor Units

Question 1

What is ALS

Answer 1

Progressive degeneration of both the UMN and LMN

Question 2

What is the finding on autopsy of ALS pt

Answer 2

Hardness of the lateral corticospinal tract.

Question 3

What is the finding on autopsy of ALS pt

Answer 3

Hardness of the lateral corticospinal tract. This hardening of the corticospinal tracts results from proliferation of astrocytes.

Question 4

In ALS besides the corticospinal tract what else is affected

Answer 4

Cell bodies of the premotor neurons in the cortex, brainstem and spinal cord degenerate progressively

Question 5

Which nerves are usually spared in ALS

Answer 5

Occular nerves and voluntary bladder control

Question 6

Which nerves are usually spared in ALS

Answer 6

Occular nerves and voluntary bladder control of spincters

Question 7

Pathophysiology of ALS

Answer 7

Loss of motor neurons in ventral spinal cord and loss of motor nuclei in lower brainstem.
Degeneration of corticospinal tracts
Loss of Betz Cells and other Pyramidal neurons in later V of motor cortex: Output neurons send axons to spinal cord.

Question 8

Symptoms of ALS

Answer 8

Firs UMN signs: 
---> Spasticity: 
     Increased muscle tone
     Hyperreflexia (Overreactive reflexes)
--> Often Babinski's sign

LMN signs:

• -> Progressive weakness of arms and legs
• -> Atrophy of muscles
• -> Fasciculations
• -> Muscle cramps

Question 9

Other ALS signs

Answer 9

Brainstem motor neurons:

• -> Respiratory muscle weakness, failure
• -> Head droop due to weak neck muscles

Other Symptoms ( Upper Motor Neurons)
Dysarthria: slurred, slow clumsy speech, weak tongue muscles
Dysphagia: dysfunction in swallowing, saliva builds up, drooling

Question 10

What is the Psuedobulbar effect

Answer 10

Lesion of the corticobulbar pathway in the brainstem. This is another result to ALS.

The corticobulbar pathway contains descending fibers that control face muscles. The results are uncontrolled bouts of laughter, crying, explosive speech without appropriate emotions = emotional incontinence.

Normal functions : Eye movements, autonomic NS ( bowel, bladder)

Question 11

TX: for ALS

Answer 11

no cure
Education, support
Drugs, PT to relieve mm cramps , fatigue
Riluzole: blocks glutamate release, may reduce damage to motor neurons. 
Antioxidants