Motor Neurone Disease

Question 1

What is an upper motor neuron?

Answer 1

Motor neuron cell bodies located in the primary motor cortex

With axons which descend as corticonuclear and corticospinal tracts

To synapse with cranial motor nerve nuclei and anterior horn cells of the spinal cord

Question 2

What is a lower motor neuron?

Answer 2

Motor neuron cell bodies of the cranial nerve nuclei and

Anterior horn cells of the spinal cord

Whose axons project to muscles via cranial nerves and spinal nerves

Question 3

What are the features of UMN lesions?

Answer 3

Weakness (distal>prox)

No wasting (delayed)

Hyperreflexia + clonus

Spastic tone

No fasciculations

Positive Babinski (extensor plantar)

Superficial abdominal and cremasteric reflexes absent

Question 4

What are the features of LMN lesions?

Answer 4

Weakness

Wasting (early)

Hyporeflexia/ areflexia

Flaccid tone

Fasciculations present

Negative Babinski (flexor plantars)

Superficial abdominal and cremasteric reflexes present

Question 5

What are motor neuron diseases?

Answer 5

Selective loss of function

Of motor neurons (UMN, LMN or combined )

Innervating voluntary muscles of the

• limbs 75%
• bulbar muscles 25%
• respiratory muscles

SPARING eye movements and sphincters

Usually relentlessly progressive

Leads to death within 5 years

Majority sporadic, rarely familial

Males > females

Question 6

How are MND classified?

Answer 6

COMBINED UMN+LMN

Classical Amyotrophic Lateral Sclerosis

PURE LMN

Symmetrical (SMA)

AR Acute infantile form
AR Chronic childhood form
Distal spinal muscular atrophy (DSMA)

Asymmetrical

progressive muscular atrophy PMA

PURE UMN 5%

Primary lateral sclerosis (limb muscles only)

Question 7

What are the signs which CANT be from MND?

Answer 7

Sensory signs

Incontinence

Ophthalmoplegia

Cerebellar signs

Extrapyramidal signs

Cognitive decline (expect FTD MND)

Question 8

What are the DDx for MND?

Answer 8

FOR ALS
Cervical spondylotic radiculomyelopathy
Spinal tumors
Conus medullaris lesion
Hyperthyroidism

FOR SMA/PMA
Poliomyelitis
Lead poisoning neuropathy

FOR PBP
CVA
MS

FOR BP
MG
Bulbar GBS
Skull base tumors

Question 10

What are the Investigations for MND?

Answer 10

EMG shows denervation with fibrillation
NCS are normal
MRI
Thyroid profile
Serum calcium

Question 11

How do you manage MND?

Answer 11

Mainly palliative and supportive

Breaking bad news , SPIKES
Nutrition PEG, caloric assessment
NIV
DNR End of life decisions

Question 12

What are the features of ALS?

Answer 12

Most common form of MND

Age of onset is 60 years

Males : females 2:1

Mostly sporadic (5% AD familial)

Present as limb onset or bulbar onset (early symptoms cramps and fatigue)

Focal , distal , asymmetrical, segmental progression

Relentlessly progressive

Mixed UMN LMN signs

Wasting (hand guttering)
Weakness (foot drop)
Fasciculations of any muscle
Hyperreflexia

BULBAR
Wasting (tongue)
Tongue fasciculations
Nasal regurgitation (palate)
Flaccid dysarthria

PSEUDOBULBAR
Dysphagia
Spastic dysarthria
Spasticity (tongue or palate)
Brisk jaw jerk
Emotional lability
Hypersalivation
Laryngospasm

Question 13

What is spinal muscular atrophy?

Answer 13

Fatal

AR

Male > female

Degenration of AHC

Symmetrical LMN wasting and weakness

Three types

Infantile

Juvenile

Adult