Page 36 - Handbook of Electronic Assistive Technology

Chapter 1 • Basic Neurosciences With Relevance to Electronic Assistive Technology 23

There are, however, a few specific clinical patterns from particular organisms that tar-
get certain groups of cells. Historically, the most significant of these is poliomyelitis, where
the poliovirus specifically infects the motor neurons leading to paralysis.
SPINAL MUSCULAR ATROPHIES
This is a group of genetic, neurodegenerative disorders of the motor neurons of the spinal
cord and brain stem. They are all linked to a specific gene area on the fifth chromosome
5q11.2-13.3.
• Selective or global muscle weakness or wasting occurs though there are a variety of
patterns, ages of presentation and severities of spinal muscular atrophy.
• The main types of spinal muscular atrophies are as follows, they are normally
recessively linked in genetic terms, requiring both parents to have the defective gene;
the lower the ‘type’ number, the earlier and more severe the presentation:
• Type 1 – seen in babies less than 6 months old.
• Type 2 – appears in babies 6–18 months old.
• Type 3 – develops after 18 months and is the least severe form in childhood.
• Type 4 – affects adults; usually only causes mild problems.
• Challenges occur primarily in motor function, but in the most aggressive form the cause
of early death is by failure of the respiratory muscles.
• A lot of trials are currently in place to try to alter the genetic defects that lead to the
destruction of motor neurons.
MOTOR NEURON DISEASES
This is a group of diseases where motor neurons are destroyed. Degeneration can occur
in motor neurons of the CNS (upper motor neurons – (UMN)), peripheral nervous sys-
tem (lower motor neurons (LMN)) or both. Signs and symptoms vary depending on which
nerves are involved but voluntary muscle activity in a variety of areas is lost.
Dependent on which motor neurons are primarily involved, symptoms include, weak-
ness, cramps and spasms, stiffness, musculoskeletal pain, immobility, clumsiness, speech,
swallowing and saliva problems and breathing problems. Emotional lability and behav-
ioural problems are also seen.
Classification is normally sporadic, but forms can also be inherited via autosomal
dominant or X-linked genetics, depending on the specific disease. Overall the relative risk
rate is about 1 in 300 in a lifetime. Inherited forms can present in early childhood but most
present after the age of 50.
Treatment is supportive at present though there are drug trials on medications that
could potentially slow the progression. Medicines to reduce pain, stiffness and improve
swallowing are used and multidisciplinary input and emotional support are vital.
Some of the most common include:

• Amyotrophic lateral sclerosis (UMN/LMN degeneration) is the commonest adult
form of motor neuron disease; onset is normally seen between 50 and 60 years. There is
involvement of all muscles, normally starting distally and working centrally. Progressive