Motor Neuron Disease

Question 1

Definition please

Answer 1

A group of several disorders where motor neurons are affected, both UPPER and LOWER.
NO SENSORY LOSS(differentiates from MS and polyneuropathies)
MND also never affects eye movements (different from myasthenia gravis)

Cause is unknown

Question 2

Epidemiology

Answer 2

very rare
M:F=3:2
Mean onset = 60
often fatal 2-3 years

Question 3

Types of MND

Answer 3

1. Amyotrophic Lateral Sclerosis (ALS) =50%
   - loss of motor neurons in motor cortex and anterior horn of spinal cord thus UMN signs and LMN wasting bilaterally
   - UMN and LMN in 3 locations
   - Bowel, bladder and eyes spared
   - split hand sign (loss of pincer grip due to wasting)
2. Progressive bulbar palsy (10%)
   - only affects CN IX-XII
   - Dysphasia, Dysphagia +/- flaccid fasciculating tongue
3. Progressive Muscular atrophy (10%)
   - ant horn lesion only, thus no UMN signs
   - Affects distal muscles before proximal
4. Primary lateral sclerosis
   - Loss of betz cells in motor cortex this mostly UMN with marked spastic leg weakness and pseudobulbar palsy

Question 4

History PC

Answer 4

> 40 years
Stumbling gait, foot drop 
Wekness 
Aspiration pneumonia 
Speech difficulty 
Swallowing difficulty 
Fronto-temporal dementia

Question 5

Examination

Answer 5

Upper and Lower Neuro and CN exam

UMN signs - spacticity, brisk reflexes, upgoing plantar

LMN signs - wasting, fasciculations

Dysphagia and dysphasia

WEAKNESS
Memory impairment

Question 6

Differential Diagnosis for NMD?

Answer 6

Peripheral neuropathies
Myopathy
Myesthenia gravis
Brain or spinal cord lesion

Question 7

Investigations

Answer 7

Brain/cord MRI to exclude structural causes
LP to exclude inflammatory causes
Nerve conduction studies to detect subclinical denervation and help exclude mimicking motor neuropathies

Question 8

Management

Answer 8

Non-Pharm

• MTD input
• blend food etc

Pharmacological
- Antiglutamatergic drugs - gives 3 months for $$$

• Amytriptyline for drooling
• analgesia for joint pain
• non-invasive ventilation