Movement Disorders Tutorial

Question 1

57M - right-handed, policeman presents complaining of tiredness, weakness in the limbs, loss of weight, breathlessness, slurred speech and difficulty swallowing.

Tiredness when walking one year ago. Before = walk miles easily, now = stops every couple miles. Legs = stiff, dragging feet, tripping easily, frequent cramps in his calves. Developed difficulty carrying things and lifting his arms. Lost 2 stone this past year, despite normal appetite. Slurring of speech, deteriorated markedly in last 6mo. Difficulty swallowing. Fluids could go down “the wrong way” and triggered coughs. Good memory and function of sphincters.

Previously healthy, no alcohol, no family history of neurological disease. 2 healthy sons.

Thin, 66 kg, 6 feet. Fully alert and co-operative. The gait was abnormal with spasticity and bilateral foot drop, uses a stick. Slurred speech and difficult to understand, but grammatically correct. Tongue wasted bilaterally, protruded outside the lips, moved v. slowly. Difficulty in drinking water - double swallow per mouthful, triggered cough. Fasciculations in tongue, palate elevated poorly with phonation, but gag reflex was pathologically brisk. Increased jaw jerk. Wasting of the shoulders, arms, forearms and legs (more on right than left in the arms and vice-versa in the legs). Widespread fasciculations in the arms, forearms, thighs and legs. Increased tone (spasticity) in limbs. Weakness in all muscle groups in the arms and legs. All deep tendon reflexes in the arms and legs were pathologically brisk. The plantar responses were extensor and abdominal reflexes were absent. All sensory modalities were preserved.

What is the diagnosis?

Answer 1

MND - motor neuron disease

Affects both, the upper and lower motor neurons:

Brisk reflexes, spasticity, muscle wastage etc.

Question 2

What are the 2 sets of symptoms applying to the upper motor neuron and lower motor neuron?

Recap of symptoms and signs: 
Brisk reflexes 
Increased tone 
Muscle atrophy
Dysarthria (difficulty speaking)
Stiff legs
Dysphagia - difficulty swallowing 
Weightloss 
Spastic movements
Slurred Speech 
Tongue Wastage 
Bilateral foot drop
Cramping calves
Weakness in limbs 
Worse on the right than left for arms 
Worse on the left than right for legs

Answer 2

Upper motor neuron symptoms:

More spastic movements - UMN sends inhibitory signals to the muscles, so degeneration of that leads to spastic muscle movement, which then increases tone
Increased tone
Dysphagia - difficulty swallowing (UMN not reaching the muscles, lack of control)
Slurred speech
Brisk (exaggerated) reflexes = muscle contracts faster and more times than normal
Stiff legs
Cramping calves - unwanted / involuntary increase in muscle tone
Inability to activate muscles

Lower motor neuron symptoms: 
Muscle atrophy - limbs
Weakness in the limbs - difficulty lifting 
Weightloss (due to muscle wastage) 
Breathlessness 
Tongue wastage 
Bilateral foot drop - muscle weakness, drags his feet around 
Dysphagia
Dysarthria (difficulty speaking)

Question 3

What pathways are affected?

Answer 3

Corticospinal - brisk reflexes
Corticobulbar - no abdominal reflex??
Rubrospinal - lower motor neurons innervating the upper limbs

Question 4

Why are the abdominal reflexes absent while the other reflexes are brisk?

Answer 4

Brisk other neurons = to do with corticospinal tract
Lack of abdominal reflex = affected corticobulbar tract

OR

Lesions in the lower motor neurons of the anterior corticospinal tract causes hyporeflexia in the abdomen

But lesion in the upper motor neurons of the lateral corticospinal tract causes hyperreflexia elsewhere

Question 5

What is a fasciculation? What is its significance?

Answer 5

Damaged motor units produce spontaneous action potentials causing a visible twitch

Question 6

How would you summarise the abnormalities in the structure and function of motor units exemplified by this case history?

Answer 6

NMD - upper and lower motor neuron damage

Question 7

Patient has weakness in the flexors of the arms and extensors of the legs.

What accounts for the difference in the weaknesses between the flexors and extensors in the upper and lower limbs?

Answer 7

Flexors in upper limb overcome gravity
But extensors in lower limb overcome gravity = easy to sit down, more difficult to stand up
Muscle wastage = weakness