Motor neurone diseases (or motor neuron diseases) (MND) are a group of neurological disorders that selectively affect motor neurones, the cells that control voluntary muscle activity including speaking, walking, breathing, swallowing and general movement of the body.
Causes
About 90% of cases of MND are "sporadic", meaning that the patient has no family history of ALS and the case appears to have occurred with no known cause. Genetic factors are suspected to be important in determining an individual's susceptibility to disease, and there is some weak evidence to suggest that onset can be "triggered" by as yet unknown environmental factors. Approximately 10% of cases are "familial MND", defined either by a family history of MND or by testing positive for a known genetic mutation associated with the disease. The following genes are known to be linked to ALS: Cu/Zn superoxide dismutase SOD1, ALS2, NEFH(a small number of cases), senataxin (SETX) and vesicle associated protein B (VAPB).
Signs and symptoms
Symptoms usually present themselves between the ages of 50-70, and include progressive weakness, muscle wasting, and musclefasciculations, spasticity or stiffness in the arms and legs, and overactive tendon reflexes. Patients may present with symptoms as diverse as a dragging foot, unilateral muscle wasting in the hands, or slurred speech. Neurological examination presents specific signs associated with upper and lower motor neurone degeneration. Signs of upper motor neurone damage include spasticity, brisk reflexes and the Babinski sign. Signs of lower motor neurone damage include weakness and muscle atrophy. Note that every muscle group in the body requires both upper and lower motor neurones to function. The signs described above can occur in any muscle group, including the arms, legs, torso, and bulbar region. The symptoms described above may resemble a number of other rare diseases, known as "MND Mimic Disorders". These include, but are not limited to, multifocal motor neuropathy, Kennedy's disease, hereditary spastic paraplegia, spinal muscular atrophy and monomelic amyotrophy. A small subset of familial MND cases occur in children, such as "juvenile ALS", Madras syndrome, and individuals who have inherited the ALS2 gene. However, these are not typically referred to as MND, but by their specific names.
Treatment
Currently there is no cure for ALS. The only drug that affects the course of the disease is riluzole. The drug functions by blocking the effects of the neurotransmitter glutamate, and is thought to extend the lifespan of an ALS patient by only a few months. The lack of effective medications to slow the progression of ALS does not mean that patients with ALS cannot be medically cared for. Instead, treatment of patients with ALS focuses on the relief of symptoms associated with the disease. This involves a variety of health professionals including neurologists, speech-language pathologists, physical therapists, occupational therapists, dieticians, respiratory therapists, social workers, palliative care specialists, specialist nurses and psychologists.
