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Flashcards in Motor neurone disease Deck (17)
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1
Q

What is the course of an upper motor neurone?

A

UMN - Cell body within primary motor cortex (pre-central gyrus of frontal cortex), axon passes through grey matter and synapses with the cranial nerve motor nuclei and the anterior horn cells in the spinal column.

2
Q

What is the course of a lower motor neurone?

A

Cell body in the anterior horn and the axon projects to the muscle cell via the nerve roots, plexi and peripheral nerves.

3
Q

What is a motor unit?

A

The motor neurone and the muscle fibre it innervates.

4
Q

What is the pathology of MND?

A

Progressive degeneration of motor neurones in the motor cortex and in the anterior horns of the spinal cord.
There is also degeneration of cells within the somatic motor nuclei of the cranial nerves within the brainstem.

5
Q

How does MND progress?

A

Usually a relentless progression of the disease towards death within 1-5 years.

6
Q

Which 4 conditions does MND encompass?

A

1) Amyotrophic Lateral Sclerosis ALS
2) Progressive Bulbar Palsy PBP
3) Primary Lateral Sclerosis
4) Primary Muscular Atrophy PMA

These are better thought of as disease features, and as the disease progresses they tend to merge.

7
Q

Does MND only affect motor neurones?

A

It is believed that other systems including cognitive centres, cerebellar, extrapyramidal pathways, as well as sensory systems can all be affected.

“A multi system disease with a predilection for motor neurones”

8
Q

Describe the aetiology and features of ALS.

A

2/100000 per year, 2:1 m:f,

Mixture of UMN and LMN signs in the limbs, head, neck and bulbar region.

Onset tends to be focal, distal and asymmetrical, progressing in a segmental fashion from one limb to another.

Also increasingly recognised that up to 50% of patients will have cognitive impairment like a frontotemporal dementia.

9
Q

Describe the features of PMA.

A

Associated with LMN signs - weakness, wasting, fasciculations, although tendon reflexes are usual maintained.

Often begins asymmetrically in the small muscles of the hands or feet and spreads.

Incorporates UMN signs in time.

10
Q

What does bulbar palsy refer to?

A

‘Bulbar’ refers to the lower brainstem motor nuclei.

A bulbar palsy usually refers to involvement of the LMN with prominent fasciculations of the tongue, often with wasting, in addition to weak palate with nasal regurgitation and nasal voice.

11
Q

What does pseudobulbar palsy refer to?

A

Pseudobulbar palsy involves the UMN bilaterally and leads to a spastic dysarthria (donald duck voice), dysphagia, hypersalivation, laryngosmpasm and emotional lability (pseudo bulbar effect)

Approx 25% of MND patients will present with bulbar onset, problematic due to risk of asphyxiation

12
Q

What are the features of primary lateral sclerosis?

A

MND patients who present with solely UMN signs, typically initially in the legs before progressing to involve the arms and bulbar region. Signs have to remain solely UMN for at least 3 years.

Progression tends to be slower and prognosis better.

13
Q

What is significant about eye movement and sphincter involvement in MND?

A

Eye movement and sphincter involvement are never affected in MND so their abnormality excludes the diagnosis.

14
Q

What is the differential diagnosis for MND?

A

Depends on the mode of presentation…

for ALS (conditions that present with UMN and LMN signs) include spinal tumours, hyperthyroidism,

for PMA (LMN signs only) include spinal muscular atrophy, poliomyositis, inclusion body myositis, lead neuropathy

for pseudobulbar (bilateral UMN lesions) incllude cerebrovascular disease, MS, Kennedy’s disease (spinal bulbar muscular atrophy)

for bulbar (LMN syndrome with no UMN signs) include myasthenia gravis, multiple lower cranial nerve lesions caused by infiltrating skull base tumours.

15
Q

How is the diagnosis of MND made?

A

Clinically, supported by electromyography EMG which shows the presence of denervation (fibrillation potentials and positive sharp waves) in the muscles supplied by more than one spinal region.
The presence of EMG changes in the tongue in association with changes in the limbs is often helpful in confirming diagnosis.
MRI of skull base and brain to exclude lesions.

16
Q

What is the treatment for MND?

A

No cure, diagnosis should be discussed along with multidisciplinary support options.

Riluzole - this is a glutamate receptor antagonist, increases survival by 2-3 months, but has no effect on disability. NICE recommends it for ALS

Symptomatic treatment -

  • speech therapy
  • reduction of salivary secretions
  • soft food or PEG tube for feeding
  • baclofen (a derivative of GABA which acts as a GABA receptor antagonist) or tizanidine (alpha 2 adrenergic agonist)
  • physiotherapy
  • Non-invasive ventilation at night
  • paliation in terminal stages
17
Q

Are sensory symptoms a common feature?

A

In pure MND, no, but up to 1/4 of patients will complain of some sensory symptoms.