Thermal threshold tester, a useful tool for detection of very early nerve damage--determination of normal values in a healthy population unexposed to Mycobacterium leprae and its application in the A9 study.
BACKGROUND
In Ethiopia, a large percentage of leprosy patients present with established nerve damage. Present techniques for measuring nerve function impairment show no abnormality until 30% of nerve axons are destroyed. Nerve damage in leprosy occurs first in small diameter unmyelinated fibres, then in small myelinated fibres, and much later in large myelinated fibres. The Thermal Threshold Tester (TTT) was used to measure function in nerves carrying heat sensation (unmyelinated C fibres) and cold sensation (thinly myelinated Adelta fibres).


METHODS
A school and community health survey, assessed 234 students and adults aged 10-75 years from Chencha Woreda, an area with low endemicity of leprosy. A group of students in Addis Ababa, exposed to leprosy, were also studied.


RESULTS
The upper limits of normal were: wrist hot threshold (HT): 0.17 degrees C, wrist cold threshold (CT): 0.19 degrees C, foot HT: 0.17 degrees C and foot CT: 0.20 degrees C. Both the leprosy group and also controls in Addis Ababa showed significantly increased TTT values.


CONCLUSIONS
The TTT detects nerve damage before clinical neuritis occurs and is a valuable tool for early diagnosis of leprosy or detecting clinical relapse of treated patients and for sequential and quantitative monitoring of small diameter nerve function in other neuropathies.
Duncan
M Elizabeth
ME
Armauer Hansen Research Institute, Addis Ababa, Ethiopia.
Hansen
Stig
S
Tadesse
Terefe
T
Bezuneh
Elisabeth
E
Yassin
Mohammed A
MA
Zeleke
Assefa
A
Solomon
Abebe
A
Jamal
Goran A
GA
Hunegnaw
Mesfin
M
Kazen
Roland
R
Aseffa
Abraham
A
Challis
Andrew
A
Wagaye
Wondu
W
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D005260:Female; D006306:Health Surveys; D006358:Hot Temperature; D006801:Humans; D007918:Leprosy / Q000150:complications*; D008297:Male; D008875:Middle Aged; D009166:Mycobacterium leprae; D009460:Neurologic Examination / Q000295:instrumentation*; D010523:Peripheral Nervous System Diseases / Q000175:diagnosis* / Q000209:etiology; D012684:Sensory Thresholds