Progressive muscular atrophy
Progressive muscular atrophy | |
---|---|
Other names | Duchenne–Aran muscular atrophy, others |
Specialty | Neurology |
Progressive muscular atrophy (PMA), also called Duchenne–Aran disease and Duchenne–Aran muscular atrophy, is a disorder characterised by the degeneration of lower motor neurons, resulting in generalised, progressive loss of muscle function.
PMA is classified among
PMA affects only the
Signs and symptoms
As a result of lower motor neuron degeneration, the symptoms of PMA include:[citation needed]
Some patients have symptoms restricted only to the arms or legs (or in some cases just one of either). These cases are referred to as flail limb (either flail arm or flail leg) and are associated with a better prognosis.[1]
Diagnosis
PMA is a
It typically takes longer to be diagnosed with PMA than ALS, an average of 20 months for PMA vs 15 months in ALS.[citation needed]
Differential diagnosis
In contrast to
- brisk reflexes
- spasticity
- Babinski's sign
- emotional lability
The importance of correctly recognizing progressive muscular atrophy as opposed to ALS is important for several reasons.
- The prognosis is a little better. A recent study found the 5-year survival rate in PMA to be 33% (vs 20% in ALS) and the 10-year survival rate to be 12% (vs 6% in ALS).[1]
- Patients with PMA do not have the cognitive change identified in certain groups of patients with MND.[3]
- Because PMA patients do not have UMN signs, they usually do not meet the World Federation of Neurology El Escorial Research Criteria for "Definite" or "Probable" ALS and so are ineligible to participate in the majority of clinical trials conducted in ALS.[1]
- Because of its rarity (even compared to ALS) 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 is likely to restrict access to services, it may be preferable to be diagnosed as "slowly progressive ALS" or "lower motor neuronpredominant" ALS.
An initial diagnosis of PMA could turn out to be slowly progressive ALS many years later, sometimes even decades after the initial diagnosis. The occurrence of upper motor neuron symptoms such as brisk reflexes, spasticity, or a
Prognosis
The 5-year survival rate has been estimated at 33% and the 10-year survival rate at 12%.[1]
History
Despite being rarer than ALS, PMA was described earlier, when in 1850 French neurologist
Disease or syndrome
Since its initial description in 1850, there has been debate in the
The neurologists
Also, no
In favour of considering PMA a separate disease, some patients with PMA live for decades after diagnosis, which would be unusual in typical ALS.[6]
To this day, terminology around these diseases remains confusing because in the
Notable cases
- Isaac W. Sprague - Entertainer and sideshow performer, billed as "the living human skeleton".
- Mike Gregory - Former Great Britain rugby league captain and head coach at Wigan RLFC
- Rob Rensenbrink - Former Netherlands and Anderlecht football player