Motor Neuron Disease

Clinic

MNDs are a group of rare neurodegenerative disorders that selectively affect motor neurons.They include

• Amyotrophic lateral sclerosis (ALS),
• Progressive bulbar palsy (PBP)
• Pseudobulbar palsy
• Progressive muscular atrophy (PMA)
• Primary lateral sclerosis (PLS)
• Spinal muscular atrophy (SMA)
• Monomelic amyotrophy (MMA)

Signs / Symptoms

UMN Sign / Symptoms

• UMN syndroms arise when the lower motor neurons cannot receive signals from the upper motor neurons. It t can cause
• Muscle stiffness (spasticity), Increased muscle tone
• Overactive reflexes, Hyperreflexia / Abnormal reflexes (Brisk reflexes, Babinski reflex, Hoffman's reflex
• This can make voluntary movements slow and difficult.
• They may lose the ability to walk or control other movements.

LMN Sign / Symptoms

Lower motor neuron syndromes may arise from pathology affecting the distal motor nerve up to the level of the anterior horn cell. They typically present with

• Muscle Wasting / Weakness / Atrophy
• Muscle twitching/ Fasciculations

• Hypotonia or atonia
• Hypo reflexia

Common symptoms:

• Gait abnormalities
• Tongue atrophy
• Upper limb and truncal muscle atrophy
• Positive Babinski sign
• Thenar muscle atrophy

• Other symptoms:
  • Exertion Dyspnea
  • Orthopnea
  • Bulbar symptoms including
    • Dysarthria
    • Dysphagia
    • Sialorrhea

• Sensation, or the ability to feel, is typically not affected

• Emotional Lability (Pseudobulbar affect)

• Cognitive and behavioural changes (Problems in word fluency, Decision-making, and Memory)

Various Patterns of weakness

• Symmetric or asymmetric
• Distal, proximal, or both

• According to Statland et al., there are three main weakness patterns:

1. Asymmetric distal weakness without sensory loss (e.g. ALS, PLS, PMA, MMA)
2. Symmetric weakness without sensory loss (e.g. PMA, PLS)
3. Symmetric focal midline proximal weakness (neck, trunk, bulbar involvement; e.g. ALS, PBP, PLS)

Classification

Type	UMN degeneration	LMN degeneration
Sporadic MNDs
ALS	Yes	Yes
PLS	Yes	No
PMA	No	Yes
PBP	Yes	Yes, bulbar region
Pseudobulbar palsy	Yes, bulbar region	No
MMA	No	Yes

Entities / Miasms

Miasms	UMN Spasm Hyper Reflexia	LMN Fasciculation Atrophy	Emotional lability	Bulbar palsy Dysarthria Dysphagia Salivation
CJD	+++	+++
PLV	+	+++		+++
GSS	+++		+++
TBE		+++	+++
NVCJD ?	+++			+++ ???