Motor Neuron Disease

Question 1

Clinical subtypes

Answer 1

ALS - amyotrophic lateral sclerosis. Mixed upper and lower motor neurone signs (upper and lower limbs), bulbar signs. If predominantly bulbar then progressive bulbar palsy (PBP)

PLS - primary lateral sclerosis. Exclusively UMN signs

PMA (progressive muscular atrophy) - LMN signs only

Question 2

Diagnosis

Answer 2

Clinical signs in keeping with the diagnoses

EMG

Exclude other causes including cervical spondylosis

Mostly sporadic but 5-10% familial (SOD1 gene in 20% of these)

Question 3

Management

Answer 3

MDT

SALT team for risk aspiration and helping communication

Dieticians - ?will need PEG

Respiratory - risk of T2RF may require NIV

Psychological

Riluzole can extend life by 3 months after 18 months administration

Question 4

Other causes of mixed motor neuropathies

Answer 4

Dual pathology ie cervical myelopathy and peripheral neuropathy disease

Cervical neuromyelopathy (spondylosis compressing roots and cord)

MND (ALS and PBP rather than PLS or PMA)

Syringomyelia/syringobulbia (dissociated sensory loss (spinothalamic tract affected when decussating at level of compression, dorsal columns unaffected) cape-like is doesn’t extend to lower limbs

Conus medullaris lesion
- can be difficult to distinguish from cauda equina. Spincter disturbance often early and prominent, inconsistent mild weakness, upgoing plantars (despite reduced reflexes)

Subacute combined degeneration of spine (B12 deficiency)
- brisk knee jerks, absent ankle, upgoing plantars, leg weakness, symmetrical peripheral neuropathy of dorsal columns, lhermittes phenomenon. Glossitis. Anaemia. Vitiligo or other autoimmune disease if pernicious anaemia

Question 5

Differential diagnosis for absent ankle jerk and upgoing plantar

Answer 5

MND
Syringomyelia
Conus medullaris lesion
Friedrichs ataxia
Subacute combined degeneration of spine
Neuro syphilus