Neuromuscular disorders
Is a term that encompasses many medical conditions/ diseases that impair the functioning of muscles either:
o Directly, which are pathologies of voluntary muscle
o Indirectly, which are pathologies of nerves or the neuromuscular junctions.
- There are four basic types of neuromuscular disorders and these involve damage to:
o Lower motor neurons, the main disorder is motor neuron disease. This is a progressive degradation of upper (brain and spinal cord) and lower motor neurons and is a relatively rare condition affecting 2 in 100,000 people a year. It also mainly affects males over the age of 50 but the course is unknown with a possible genetic link (family history in 5% of cases). It has a low survival rate with most living for about 3 years after diagnosis, however some patients may live up to 10 years or longer in rarer cases. The main symptoms include:
§ Weakness and wasting of muscles of limbs, trunk and neck
§ Bulbar muscle (pharynx and soft palate) palsy, which can lead to problems with speaking, swallowing and chewing.
§ Respiratory difficulties, due to the nerves and muscles involved in respiration are affected
§ However the sensory system is not affected, sight, hearing, sensation not involved).
There is no current cure for the condition and so the treatments are palliative, aimed at reliving symptoms and slowing disease progression and these treatments include:
§ Riluzole, which slows down progressive damage to motor neurons by reducing their sensitivity to glutamate.
§ Drugs can also be given to help with muscle spasticity (stiffness) and drooling
§ Ventilatory support for respiratory difficulties and feeding by a gastrotomy.
§ Physiotherapy, occupational therapy and speech therapy
o Neuromuscular junctions the main damage is by Myasthenia Gravis and is an autoimmune condition, leads to neuromuscular transmission often failing. In about 90% of patients generating antibodies against their own nicotinic Acetylcholine receptors at the motor end plate, and these antibodies bind to the receptors and this interferes with normal actions of Acetylcholine at the neuromuscular junctions. It can also lead to the end plate also being damaged in longer term. However it is an uncommon disease affecting about 4 in 100,000 and mainly occurs in younger females with a peak age of 30, however there can also be late onset affecting elderly men over 60. It is with hyperplasia, which is the enlargement of the thymus gland and thymoma which is tumours of the thymus. Common symptoms can include fatigue in many muscles with the most commonly affected being:
§ Eyes, can have diplopia which is double vision, ptosis which is dropping of upper eye lid , and eye closure weakness.
§ Bulbar muscles, which are pharynx and soft plate and can lead to problems with speaking, swallowing and chewing
§ Weak arms, legs and neck
§ Respiratory difficulties
Treatments can include:
§ Corticosteroids, to reduce the inflammation
§ Immunosuppressive drugs, to dampen down the antibodies being produced
§ Acetylcholinesterase inhibitors, prevents Acetylcholine form being broken down so quickly so it can bind to receptors not blocked
§ Removal of antibodies by plasma exchange
§ Thymectomy, removal of thyroid gland.
o Muscles with the main disorder being Duchenne muscular dystrophy, this is progressive degeneration and weakness of muscle and is an inherited disease being X linked and so usually of affects boys. It affects 1 in about every 3500 – 5000 male births and caused by a mutation in dystrophin gene – leading to the dynorphin protein being absent or non-functioning. The protein is very large and does the job of connecting the cytoskeleton of the muscle fibres to the surrounding extracellular matrix through the cell membrane, this allows to help maintain the structural integratory and so without it the muscle fibres are susceptible to cell membrane rupture and cell death (apoptosis). Symptoms in children include:
§ Difficulty walking, running or jumping
§ Difficulty standing up
§ Be unable to climb the stairs without support
§ Mild developmental delay
Generally the patients require a wheelchair by teens and only live up to the age of 30 years old. Unfortunately there is no cure for the disorder and so treatment is aimed at managing the condition such as:
§ Physiotherapy and occupational therapy, to help patients to keep their independence for as long as possible
§ Ventilatory support if muscles of diaphragm are affected
§ Corticosteroids, to help improve muscle strength and slow muscle weakness.
o Peripheral nerves the main damage by neuropathy’s which are nerve diseases, this can encompass a wide range of different diseases but results in damage to one or more nerves and results in clinical features that reflect this damage to those nerves such as:
§ Mononeuropathy, which is single nerve damage by compression such as carpel tunnel syndrome. It is the median nerve which is affected in carpel tunnel syndrome by compression and is a major peripheral nerve the upper limb, it is responsible for innervating most of the flexor muscles of the anterior forearm and hand muscles. The carpel tunnel itself is a thick ligament which the median nerve passes through. There is Increased risk of developing this injury from:
· Strenuous, repetitive work
· Arthritis
· Pregnancy, due to hormonal changes and extra fluid retention.
· Diabetes
· Obesity
· Hand injuries, such as: sprain, fracture or crush injury
§ The main symptoms can include:
· Tingling, numbness and pain in one or both hands
· Hand weakness
· Wasting away (atrophy) of muscle at base of thumb known as the thenar eminence
· Pain is often worse at night or early in the morning
§ Treatments for carpel tunnel syndrome can include:
· Wrist splints
· Local steroid injections
· As a last resort can have carpel tunnel release surgery, cut made in carpel tunnel ligament to release pressure on the median nerve.
§ Mononeuritis multiplex, which have serval nerves involved such as vasculitis (inflation of skull)
§ Polyneuropathy, this involves many nerves such as Guillain-bare syndrome.