Multiple sclerosis

Multiple sclerosis is one of the most common causes of chronic neurological disability in young adults. It is characterised by widespread foci of demyelination, followed by a gliosis ( the proliferation of different form of cell known as the astrocyte - these cells also have long thin processes but do not form myelin.), within the nervous system. The number and distribution of areas of demyelination, known as plaques, varies considerably from case to case and it typically presents with symptoms and signs that fluctuate over many years, often several decades, and with each exacerbation new signs appear and old signs may worsen. There is a progressive downhill course. Patients usually present with a single focal neurological deficit which then remits for variable periods of time before the appearance of a further episode. A few cases follow a progressive course from onset without remission. The focal neurological defects usually develop rapidly over a period of a few hours or days.

Symptoms and signs

The most common symptom is that of weakness of limbs. This may commence as a feeling of heaviness or fatigability which varies in rate of onset or progression. Involvement of the lower limbs is the most common but upper limbs and face may be involved in some cases. Sensory abnormalities occur at some stage in the disease in most cases which often take the form of numbness or tingling and may include disturbance of fine sensibility, joint and position sense, and the sense of vibration.

Approximately 30% suffer visual symptoms such as blurring of vision, double vision, dimness of vision and/or a visual field defect. Retrobulbar neuritis, usually initially acute and unilateral, is often an early symptom, with misty vision progressing rapidly to perception of light and movement only, is common. The eye may be painful on movement and tender on pressure. Although this may improve rapidly it tends to leave some optic atrophy with pallor of the disc. Deterioration of vision may continue although blindness is uncommon. It is important to realise that considerable abnormalities of visual fields may be present without the patient being aware of it.

Nystagmus is often seen and usually appears on conjugate deviation laterally. A variety of ocular movement disorders may be seen, depending upon the site of demyelination. Pupillary reactions are usually normal but can occur.

Vestibular symptoms, such as vertigo, are common and there may be disturbance of hearing, although cortical deafness is rare.

Sphincter control is frequently impaired and some patients may show evidence of autonomic dysfunction, including abnormalities within the cardiovascular system.

Some reduction in intellectual capacity is common and emotional changes are frequent. This may progress to dementia in the late stages.

The course of the disease varies considerably from death within a few months to death from another cause following asymptomatic survival. The average life span is about 25 years.