Tropical ataxic neuropathy

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Tropical ataxic neuropathy
Other namesStrachan-Scott syndrome and prisoners of war neuropathy
SpecialtyNeurology

Tropical ataxic neuropathy (TAN, also known as Strachan-Scott syndrome and prisoners of war neuropathy) is a disease or category of diseases that commonly causes disability and increases mortality. The causes of TAN are not understood; there is no generally accepted treatment, and the reported outcomes are inconsistent.[1]

The disease affects poor tropical populations; there are no good statistics on how many people are affected worldwide, but in some populations, more than a quarter of people are affected.[1] Malnutrition may play a role.[2]

TAN is one of many

tropical myeloneuropathies. It was first described in Jamaica in 1897, by postmortems of 510 cases; in 1959, it was dubbed "tropical ataxic neuropathy".[1]

Epidemiology

TAN has only been described as developing in Africa, South-east Asia, and the Caribbean (if

temperate countries.[1] People affected by TAN tend to be poor and live in rural areas.[3] In some areas, more than a quarter of the population are affected. In India and Africa, more women are affected; in Africa, the elderly are most likely to suffer, and in India, people in their thirties. Historical data suggests that, in the 1960s, TAN in Africa was most common in people in their 30s and 40s.[1]

While the areas affected roughly correspond to the areas in which cassava is grown, some people in non-cassava-growing populations get TAN, and some cassava-growing populations do not get TAN.[4][1] It is possible that there are several diseases being categorized as TAN.[1]

It has been estimated that 5% of surviving World War II

prisoners of war held in the Far East acquired TAN; while they were held for 3.5 years or less, the TAN symptoms persisted chronically after they returned to temperate climates.[5]

Causes and symptoms

The causes of TAN are unclear; there may be several separate causes of similar symptoms.

There are thought to be two neurological syndromes lumped together as TAN. One affects adolescents, appears with

retrobulbar optic neuropathy and evidence of malnutrition, and improves with better nutrition. Half of these adolescents are seen to have spinal ataxia.[1]

The other affects middle-aged and elderly people. They suffer

pyramidal tract of the spinal cord. For these older patients, evidence of malnutrition is rarer, and improving nutrition does not improve symptoms.[1]

Most of those with the older-onset form have symptoms in their legs, but a third to a half also have arm symptoms. Symptoms tend to worsen during the

dysphonia (difficulty speaking); dysphonia is more common in women, and shows as hypophonia (lack of co-ordination in the vocal cords) and an inability to shout.[1]

Diagnosis

The diagnostic criteria were defined in 1968.

pyramidal tract myelopathy, with ataxic polyneuropathy". The classification of TAN is still not settled, and researchers disagree about it.[1]

Treatment

Nutritional improvements; supplying nutritional yeast, teaching improved cassava preparation,[1] and ceasing cassava consumption.[3]

Outlook

Unclear, with contradictory reports from different studies.[1]

Research directions

A 2016 review listed twenty-one open research questions.[1] The value of international co-operation on TAN research has also been highlighted.[7]

Other animals

The behaviour and neurology of malnourished and cassava-fed rats has been compared to that of humans with TAN.[1]

See also

References

  1. ^
    PMID 27841178
    .
  2. ISBN 978-0-19-971004-1
    . Retrieved 12 March 2020.
  3. ^
    PMID 28904445
    .
  4. S2CID 19377135
    .
  5. PMID 18854350
    .
  6. PMID 5673206
    .
  7. S2CID 20850916
    .
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