Progressive Spinal Muscular Atrophy

Definition

Definition of Progressive Spinal Muscular Atrophy
Progressive muscular atrophy (PMA) is a rare subtype of amyotrophic lateral sclerosis (ALS) or motor neurone disease (MND) which affects only the lower motor neurones. PMA is thought to account for around 4% of all ALS/MND cases. This is in contrast to the most common form of ALS/MND, amyotrophic lateral sclerosis, which affects both the upper and lower motor neurones, or another rare form of ALS/MND, primary lateral sclerosis, which affects only the upper motor neurones. The distinction is important because PMA is associated with a better prognosis than classical ALS/MND.

Symptoms

Symptoms of Progressive Spinal Muscular Atrophy
As a result of lower motor neurone degeneration, the symptoms of PMA include:

1. atrophy
2. fasciculations
3. muscle weakness

Causes

Causes of Progressive Spinal Muscular Atrophy
Consult with your doctor.

Diagnosis

Diagnosis of Progressive Spinal Muscular Atrophy
PMA is a diagnosis of exclusion, there is no specific test which can conclusively establish whether a patient has the condition. Instead, a number of other possibilities have to be ruled out, such as multifocal motor neuropathy or spinal muscular atrophy. Tests used in the diagnostic process include MRI, clinical examination, and EMG. EMG tests in patients who do have PMA usually show denervation (neurone death) in most affected body parts, and in some unaffected parts too.

Treatment

Treatment of Progressive Spinal Muscular Atrophy
A small, but significant effect of the glutamate-inhibitor riluzole on survival in ALS has been demonstrated in two randomized, double blind, placebo-controlled, clinical trials. Patients with PSMA were included into the category ‘suspected ALS’ according to the (1994) El Escorial criteria. However, this subgroup was omitted in the (1998) revised El Escorial criteria. As a result, patients with PSMA are not included in ALS research studies. Since progression in PSMA can be as rapid as in ALS we recommend that patients with ALS-like PSMA are treated with riluzole. Even slowly progressive forms of PSMA can ultimately evolve to severe disability and respiratory insufficiency. Therefore, it might well be that these patients could also benefit from treatment with the glutamate-inhibitor riluzole, although there are no robust data to corroborate this assumption. With regard to the care of PSMA patients at multidisciplinary ALS/MND clinics and the management of symptoms.

Prognosis

Prognosis of Progressive Spinal Muscular Atrophy
The importance of correctly recognizing progressive muscular atrophy as opposed to ALS/MND is important for several reasons.

1. the prognosis is a little better. A recent study found the 5-year survival rate in PMA to be 33% (vs 20% in ALS/MND) and the 10-year survival rate to be 12% (vs 6% in ALS/MND).
2. Patients with PMA do not suffer from the cognitive change identified in at least a subgroup of patients with ALS.
3. Because PMA patients don’t have UMN signs, they usually do not meet the "World Federation of Neurology El Escorial Research Criteria" for “Definite” or “Probable” ALS/MND and so are ineligible to participate in the majority of clinical research trials such as drugs trials or brain scans.
4. Because of its rarity (even compared to ALS/MND) and confusion about the condition, some insurance policies or local healthcare policies may not recognize PMA as being the life-changing illness that it is. In cases where being classified as being PMA rather than ALS/MND is likely to restrict access to services, it may be preferable to be diagnosed as "slowly progressive ALS/MND" or "lower motor neurone predominant" ALS/MND.

Prevention

Prevention of Progressive Spinal Muscular Atrophy
Consult with your doctor.