A case of Tropical ataxic neuropathy

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Tropical ataxic neuropathy is endemic to certain parts of the world and is causally related to the regular long term intake of cassava. The Cyanogen, Linimarin and its subsequent metabolism leading to the release of cynanide and thiocyanate and the development of deficiency of sulphur containing amino acids lead to the neurotoxicity which presents as predominant sensory neuropathy with ataxia. We report a young patient from Tanzania with the disease and highlight the importance of dietary history in patients with unexplained neurological illness.

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A case of Tropical ataxic neuropathy

  1. 1. A case of Tropical ataxic neuropathy
  2. 2. Case Report A case of Tropical ataxic neuropathy V.L. Arul Selvan Consultant Neurologist, Apollo Institute of Neurosciences, Chennai, India a r t i c l e i n f o Article history: Received 23 July 2013 Accepted 7 August 2013 Available online 31 August 2013 Keywords: Tropical ataxic neuropathy Cyanide Tanzania a b s t r a c t Tropical ataxic neuropathy is endemic to certain parts of the world and is causally related to the regular long term intake of cassava. The Cyanogen, Linimarin and its subsequent metabolism leading to the release of cynanide and thiocyanate and the development of deficiency of sulphur containing amino acids lead to the neurotoxicity which presents as predominant sensory neuropathy with ataxia. We report a young patient from Tanzania with the disease and highlight the importance of dietary history in patients with unex- plained neurological illness. Copyright ª 2013, Indraprastha Medical Corporation Ltd. All rights reserved. 1. Case report A 19 year old gentleman from Tanzania came to Apollo Hos- pitals, Chennai with a history of progressive unsteadiness of walking of 3 years duration which was insidious in onset. He gave history of numbness of feet which spread gradually to his legs and to his right thigh of 2 1/2 years duration. He felt more unsteady in the dark and during the day, he was mostly in- doors as he needed support to walk on the road. He had burning sensation and paresthesis initially, which have reduced subsequently. He also had increased sweating all over his upper body. He did not have any weakness but had slip- ping of his chappals without his awareness. He had no thin- ning of muscles or twitching but had occasional calf cramps. He had no symptoms referable to the higher Cognitive func- tions, Cranial nerves, Upper limbs, neck or trunk. He had no bowel or bladder related symptoms or orthostatic giddiness. He had hypopigmented, macular skin lesions over the neck, upper limbs and trunk but no nail or mucosal symptoms. There were no constitutional symptoms. There was no history of similar symptoms in the family or immediate neighbourhood. On examination, he had extensive Taenia versicolor, perhaps due to the excessive sweating but no other mucocu- taneous lesions. He was moderately nourished and general physical examination was otherwise normal. Neurological examination revealed normal higher cogni- tive functions and Cranial nerve examination including Fundus were normal. There was no muscle wasting and there was minimal toe grip weakness. The abdominal reflex was present and plantars were flexor. The Deep tendon re- flexes were normal in the Upper limbs, Knee jerks were reduced and Ankle jerks were not elicitable. There were intermittent coarse neuropathic tremors involving the left toes. There was graded sensory loss involving Touch, pain, temperature, Vibration and position sense below the knee. The gait was broad based and ataxic and there was marked worsening of balance on eye closure. There was no nerve thickening. A diagnosis of predominantly sensory progres- sive polyneuropathy was made and the patient was investigated. Nerve conduction study revealed absent sensory re- sponses in all four limbs. The motor responses were normal in the Upper limbs. In the lower limbs, the DMLs were E-mail address: drarulselvan@yahoo.com. Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/apme a p o l l o m e d i c i n e 1 0 ( 2 0 1 3 ) 2 2 3 e2 2 5 0976-0016/$ e see front matter Copyright ª 2013, Indraprastha Medical Corporation Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apme.2013.08.007
  3. 3. borderline, the CMAP amplitudes were reduced and the CVs were mildly reduced. The Right Tibial f wave latency was prolonged and the other f waves were normal. The RR in- terval variability was normal, but the Sympathetic skin response was absent. The NCS features were suggestive of a predominantly sensory polyneuropathy with autonomic neuropathy involving the sympathetic component and the motor abnormalities pointed to a predominantly axonal process. The VEP revealed prolongation of the P100 latencies on either side. His blood investigations including ESR, CRP and Vasculitis package were normal. HIV and HTLV 1 and 2 antibodies were negative. His MRI Brain and CSF study were normal. His Audiometry was normal. A detailed dietary history was undertaken. The patient said that he has been eating Cassava daily for several years. The Cassava was boiled, cut into pieces, fried and eaten. The other family members, though used to consume Cas- sava, did so about twice a week, where as the patient was taking it daily, as he was fond of it. He denied that anyone else in the family or immediate neighbourhood had a similar illness. A nerve and muscle biopsy were done. The muscle bi- opsy from the vastus lateralis showed features of early denervation without any inflammatory changes. Sural nerve biopsy revealed shows 3e4 fascicles enclosed by thick epineurium. There was marked loss of large and small diameter fibres in all fascicle with several bands of bungner but no axonal regeneration. The fibre loss was overall uni- form but focally within fascicle it was in pockets. Few fibres had thick myelin (architecture) epi and endoneurial small vessels showed thickening reflecting chronicity. No vascu- litis was noted. Impression: Chronic axonopathy without regeneration e consistent with nutritional/Tropical ataxic neuropathy. Based on the Dietary history, typical clinical features and nerve biopsy features a diagnosis of Tropical ataxic neuropa- thy (TAN) was made. The patient was strongly adviced to stop consuming Cassava and was prescribed S-adenosyl methio- nine, neurotropic vitamins and Cap Astymin forte (Essential Aminoacids). 2. Discussion Cassava, also called Tapioca or manioc, is a staple food for over 600 million people around the globe and especially in the Tropics. The crop variety is a tuber and it is resistant to drought, plant diseases, insects and animal predators8 and needs relatively little water to survive and hence represents an extremely valuable crop for subsistence.9 Cassava con- tains a cyanogenic compound Linimarin which releases cy- anide which is neurotoxic.6 Usually cassava is processed by powdering and drying which helps to reduce the cyanide content considerably. However, during famine or due to personal preference, if proper processing is not done, the propensity to build toxic levels in the body increases. During famine, when cassava is consumed in large quantities, leads to a condition called Konzo. Here, there is severe involvement of the corticospinal tract and patients present with subacute onset of spastic paraplegia which resembles Lathyrism. When the toxic dose is small and the exposure is for a prolonged period, patients develop Tropical ataxic neuropathy. The incidence of Konzo and Tropical ataxic neuropathy can be as high as 3% in some places in Africa. The four cardinal features of Tropical ataxic neuropathy are 1. Severe sensory ataxia, due to involvement of the sensory ganglion or posterior column. 2. Predominantly sensory pe- ripheral neuropathy. 3. Optic neuropathy. 4. Sensorineural deafness.1 The presence of any two of the above with appropriate dietary history is sufficient to make the diag- nosis of Tropical ataxic neuropathy. In a study of 206 pa- tients in Nigeria,9 glove and stocking sensory impairment of pain and touch sensibilities were found in 202 (98%), sensory gait ataxia in 172 (84%), optic atrophy in 98 (48%), and neurosensory deafness in 40 (19%).3 The disease manifested mostly during the 4th decade, however it can start from 8 years to 60 years of age. In one study Knee jerks were absent or diminished in 76% of patients and was normal in 24%.4 Vitamin deficiencies did not play a significant role in any of the studies on TAN,5 but deficiencies of sulphur contain- ing amino acids (which are essential for detoxifying cyanide) were found in studies.7 In India, cassava is consumed mainly in Kerala among the lower socioeconomic strata and Dr Madhusudhan et al have published a large series of 40 patients with Tropical ataxic neuropathy. In their series, all had sensory polyneuropathy, 90% had sensory deafness, 50% had visual impairment and 25% had spasticity involving the lower limbs. Increased levels of thiocyanate were demonstrated in the Urine, serum or sural nerve specimens.2 In this era of Medical tourism, when we encounter patients from other countries, it appears essential to have an idea about the dietary habits and common neurological disorders prevalent in such countries. Conflicts of interest The author has none to declare. r e f e r e n c e s 1. Dobbs Michael R. Textbook of Clinical Neurotoxicology. 1st ed. Saunders; 2009. 2. Madhusudanan M, Menon MK, Ummer K, Radhakrishnanan K. Clinical and etiological profile of tropical ataxic neuropathy in Kerala, South India. Eur Neurol. 2008;60(1):21e26. 3. Oluwole OS, Onabolu AO, Link H, Rosling H. Persistence of tropical ataxic neuropathy in a Nigerian community. J Neurol Neurosurg Psychiatr. 2000 Jul;69(1):96e101. 4. Roma´n GC, Spencer PS, Schoenberg BS. Tropical myeloneuropathies: the hidden endemias. Neurology. 1985 Aug;35(8):1158e1170. 5. Osuntokun BO, Aladetoyinbo A, Bademosi O. Vitamin B nutrition in the Nigerian tropical ataxic neuropathy. J Neurol Neurosurg Psychiatr. 1985 Feb;48(2):154e156. a p o l l o m e d i c i n e 1 0 ( 2 0 1 3 ) 2 2 3 e2 2 5224
  4. 4. 6. Makene WJ, Wilson J. Biochemical studies in Tanzanian patients with ataxic tropical neuropathy. J Neurol Neurosurg Psychiatr. 1972 Feb;35(1):31e33. 7. Osuntokun BO, Durowoju JE, McFarlane H, Wilson J. Plasma amino-acids in the Nigerian nutritional ataxic neuropathy. Br Med J. 1968 Sep 14;3(5619):647e649. 8. Tshala-Katumbay D, Mumba N, Okitundu, et al. Cassava food toxins, konzo disease, and neurodegeneration in sub-Sahara Africans. Neurology. 2013;80:949e951. 9. Osuntokun BO. An ataxic neuropathy in Nigeria: a clinical, biochemical and electrophysiological study. Brain. 1968;91(2):215e248. a p o l l o m e d i c i n e 1 0 ( 2 0 1 3 ) 2 2 3 e2 2 5 225
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