Tropical Myeloneuropathies Clinical Presentation

Updated: Apr 13, 2021
  • Author: Emad R Noor, MBChB; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
  • Print


Tropical ataxic neuropathy (TAN)

See the list below:

  • Difficulty walking

  • Burning pain in the hands and feet

  • Amblyopia (in some prisoner-of-war camps, as many as two thirds lost vision)

  • Subacute or chronic onset

HTLV-1–associated myelopathy/tropical spastic paraparesis (HAM/TSP)

See the list below:

  • Presenting neurological symptoms in 80% of cases - Gradual onset of leg weakness, back pain, paresthesias, and impairment of urinary or bowel function

  • Erectile dysfunction possible - In one case report, the presenting symptom

  • Increased urinary frequency

  • Dermatitis [9] or psoriasis [10]



Tropical ataxic neuropathy (TAN)

See the list below:

  • Impaired light touch and vibration sensation and proprioception

  • Gait ataxia

  • Romberg sign

  • Hyporeflexia or areflexia

  • Sensorineural hearing loss

  • Muscle weakness and atrophy that can involve upper extremities

  • Similar symptoms were described among prisoners of war in the tropical and subtropical regions.

HTLV-1–associated myelopathy/tropical spastic paraparesis (HAM/TSP)

See the list below:

  • Spastic paraparesis or paraplegia with hyperreflexia, clonus, and extensor plantar responses; weakness of the lower extremities, more marked proximally

  • Decreased touch and pinprick sensation in poorly defined thoracic areas

  • Vibration sensation frequently impaired, especially in the lower extremities, resulting from spinal cord or peripheral nerve involvement [11]

  • Low lumbar pain with radiation to the legs

  • Hyperreflexia of upper extremities frequently associated with Hoffmann sign

  • Less frequent neurological findings - Cerebellar signs (ie, intentional tremor, dysmetria), optic nerve atrophy, deafness, nystagmus, cranial nerve deficits, upper extremities tremor, absent or diminished ankle jerk

  • Increased urinary frequency - Due to detrusor hyperreflexia (ie, neurogenic bladder) associated with increased incidence of urinary tract infection



Tropical ataxic neuropathy (TAN)

In many cases, TAN is associated with excessive consumption of cassava, also known as the mandioca or tapioca plant, which is one of the most important sources of calories in the tropical countries. About 300 million people depend on it for subsistence, especially in the tropical regions of the Americas and in Africa. Cassava contains cyanide in the form of a cyanogenic glycoside, linamarin, which releases cyanide by the enzymatic action of linamarinase or by hydrolysis. Chronic cyanide intoxication has been confirmed as the cause of the TAN described in Nigeria and Tanzania. In these patients, treatment with high-dose vitamins was not satisfactory, suggesting that the vitamin deficiencies are not important in the etiology of the disease in these cases. There are two neurological disorders associated with cassava consumption: tropical ataxic neuropathy (TAN) and epidemic spastic paraparesis (konzo). Konzo is a syndrome that mainly affects young women and children. [12]

Processing of the cassava flour removes almost all the cyanide, but during a drought, these procedures tend to be shortened or ignored. Many people, especially women and children, eat the cassava raw or merely sun dried. The cyanide content of cassava increases during a drought, which may lead to a relatively higher incidence of severe cyanide intoxication.

Vitamin deficiencies and tropical malabsorption were the causes of TAN in prisoners of war. In most of the cases, the affected individuals were deficient in group B vitamins. One literature review suggests that chronic thiamine deficiency has a strong correlation with TAN. [1]

HTLV-1–associated myelopathy/tropical spastic paraparesis (HAM/TSP)

TSP is caused by an infection with HTLV-1.

Cases of TSP have been documented in which HTLV-1 was not detected.