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.

1. A case of Tropical ataxic neuropathy

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.
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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
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2. Madhusudanan M, Menon MK, Ummer K,
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ataxic neuropathy in Kerala, South India. Eur Neurol.
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3. Oluwole OS, Onabolu AO, Link H, Rosling H. Persistence of
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myeloneuropathies: the hidden endemias. Neurology. 1985
Aug;35(8):1158e1170.
5. Osuntokun BO, Aladetoyinbo A, Bademosi O. Vitamin B
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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
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8. Tshala-Katumbay D, Mumba N, Okitundu, et al. Cassava food
toxins, konzo disease, and neurodegeneration in sub-Sahara
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