Motor Neuron Disease

Motor Neuron Disease

• Incidence: 2-4 per 100 000

• Onset: usually 50-70 years

• Pathology: – Degenerative condition

– anterior horn cells and upper motor neurons in spinal cord, resulting in mixed upper and lower motor neuron signs

• Cause unknown– 10% familial (SOD-1 mutation)

– ? Related to athleticism

Presentation

• Several variations in onset, but progress to the same endpoint

• Motor nerves only affected• May be just UMN or just LMN at onset, but other

features will appear over time

• Main patterns:– Amyotrophic lateral sclerosis– Bulbar presentaion– Primary lateral sclerosis (UMN onset)– Progressive muscular atrophy (LMN onset)

Questions

Wasting

Classification

• Amyotrophic Lateral Sclerosis

• Progressive Bulbar Palsy

• Progressive Muscular Atrophy

• Primary Lateral Sclerosis

• Multifocal Motor Neuropathy

• Spinal Muscular Atrophy

• Kennedy’s Disease

• Monomelic Amyotrophy

• Brachial Amyotrophic Diplegia

El Escorial Criteria for Diagnosis

Tongue fasiculations

Amyotrophic lateral sclerosis

• ‘Typical’ presentation (60%+)• Usually one limb initially

– Foot drop– Clumsy weak hand– May complain of cramps

• Gradual progression over months

• May be some wasting at presentation• Usually fasiculations (often more widespread)• Brisk reflexes, extensor plantars• No sensory signs; MAY occasionally be mild symptoms

• Relentless progression, noticable over weeks/ months

Bulbar MND

• Approximately 30% of cases

• Onset with dysarthria, dysphagia

• Bulbar and pseudobulbar symptoms

• On examination– Dysarthria

– Tongue wasting, fasciculation

– Brisk jaw jerk

– May be other limb symptoms (but not always)

• Progression more rapid than ALS presentation

• Worse prognosis (approx 2 years)

Other presentations

• Primary lateral sclerosis (5%)

– Pure UMN onset

• Progressive muscular atrophy (5%)

– Pure LMN onset

– May be ‘flail limb’ appearance

• Probably slightly better prognosis

Progressive bulbar palsyDifficulty breathingMuscle weakness

Motor neuron disease II

Differential diagnosis

• Diagnosis is clinical– EMG/ imaging may help

• MND is fatal – exclude other, less severe/treatable conditions

– Multilevel cervical/ lumbar degerative changes• May cause myelopathy + LMN features and fasciculation• Usually have sensory symptoms

– Benign fasciculation syndrome – Bulbar – cerebrovascular disease, MND

– Multifocal motor neuropathy– Hereditary spastic paraplegia– Kennedy’s disease (SMA)

Investigations

• Clinical diagnosis

• Check CK – modest elevation

• Investigations often aimed at excluding other causes– Often MRI cervical/lumbar spine– May image brain

• NCS/ EMG show “chronic active denervation” in areas supplied by multiple nerve roots (note this pattern may be seen in one territory by radiculopathy)

• Tongue/ Sternomastoid EMG sometimes performed

Treatment

• Riluzole– Glutamate antagonist – May extend left expectancy slightly (3-5 months on average)

– Low side effect profile• Occ nausea, fatigue• Can disturb LFTs (needs monitoring at onset)

– Expensive (?cost/ benefit)

• Palliative– Nutrition

• Soft diet• ‘Chin tuck’

– Hyoscine (excessive secretions/salivation)– Opiates/ benzodiazepines

MND dementia

• Proportion of patients develop frontotemporal dementia

– Flat affect

– Disinhibition

– Language disturbance/ dysphasia

– Impaired ‘executive function’

Cervical spondylomyelopathy vs Motor neuron disease

• Flaccid weakness UL, shoulder girdle

• Wasting of all small hand muscles

• Inverted supinator

• MyeloCT scan – spinal stenosis C4-C6

• EMG – denervation of UL muscles

Motor Neuron Disease

• Look for signs• Differential diagnosis• Counselling

• Good luck