Motor Neuron Disease

Question 1

What is the life expectancy of MND?

Answer 1

3-5 years from diagnosis

Question 2

What is the most common age of onset of MND?

Answer 2

60-80 years

Question 3

What are the 2 most common presentations of MND and their frequency?

Answer 3

Asymmetric limb weakness (80%)
Bulbar weakness (20%) - impairment of function of cranial nerves 9,10,11 and 12

Question 4

What are some bulbar upper motor neuron signs?

Answer 4

Dysarthria (high pitched speech)
Increased jaw jerk
Dysphagia due to spasm
Laryngospasm
Pseudo bulbar affect (“emotional incontience”)
Increased jaw spasticity and difficulty opening jaw

Question 5

What’s are some limb upper motor neuron signs?

Answer 5

Stiffness
Spasticity
Hoffmans sign (flicking 3rd digit will lead to contraction of thumb and second digit)
Babinski's
Increased reflexes
Spontaneous clonus
Flexor spasms
Difficulty manipulating small objects

Question 6

What are some bulbar lower motor neuron signs?

Answer 6

Dysarthria (slurred speech dispute to tongue and cheek weakness)
Tongue fasiculations and atrophy
Weak mass enter muscle (weak chewing)
Weak pharyngeal muscles (risk of aspiration)

Question 7

What are some limb lower motor neuron signs?

Answer 7

Split hand syndrome (wasting of thenar and first interossei with sparing of hypo thenar (doesn't fit with peripheral nerve lesion)
Fasicluations
Cramps
Foot drop
Decreased reflexes
Difficulty rising from a chair
High stepping gait

Question 8

What is central to the clinical suspicion of motor neuron disease?

Answer 8

Upper motor neuron and lower motor neuron signs

Question 9

What type of dementia is associated with MND?

Answer 9

Fronto-temporal dementia

• 5-10% MND have FTD
• 30-40% have cognitive impairment

Question 10

What are the main subtypes of MND and their main feature?

Answer 10

Amyotrophic lateral sclerosis - most common, UMN and LMN
Progressive bulbar palsy - 20% have predominant bulbar signs, mostly females, worse prognosis
Primary lateral sclerosis - upper motor neuron signs only
Progressive muscular atrophy - lower motor neuron signs only
Flail arm syndrome - LMN signs in arm with positive Babi ski
Flail leg syndrome - as above but in leg
ALS-plus syndromes - ALS with features that would typically exclude the diagnosis (sensory change, ataxia, parkinsonsism, eye signs)

Question 11

What are the pathological features of MND?

Answer 11

Pathological inclusions of ubiquitin, TAR-DNA binding protein (TDP-43)and fused in sarcoma protein (FUS)
Anterograde neuron cell death due to glutamate excitotoxicity

Question 12

What proportion of MND is familial and what genes are implicated?

Answer 12

10%

Autosomal dominant - SOD-1 and TDP-43

Question 13

What are the tests recommend for diagnosis of MND?

Answer 13

Testing is more about excluding treatable causes
EMG + nerve conduction studies will show signs of nerve denervation and fibrillation potential, only evaluates lower motor neuron signs
MRI brain and spinal cord - to exclude nerve root compression
Blood test - vitamin deficiencies, anti-GM1 (multifocal motor neuropathy), anti-Musk and anti-AchR antibodies, autoimmune screen, TFTs, protein electrophoresis

Question 14

What is the only possible disease modifying treatment of MND?

Answer 14

Riluzole

• reduces glutamate and excitotoxicity
• small benefits in survival
• funded in aus/nz for this with less than 5 years disease and no ventilatory requirements

Question 15

What are some non-pharmacological interventions that can improve survival?

Answer 15

NIV

PEG insertion