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ТОМ 6, СТ. 156 (стр. 498-499) // Март, 2005г.

H-reflex latency changes during the Parkinson disease.

Voitenkov V., Borisova E.
Institute of Experimental Medicine, St.-Petersburg Neurology Clinic

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Parkinson's disease is a severe progressive condition of a nervous system, characterized not only with a lesion of extrapyramidal system, but also with a changes of functioning of spinal cord and peripheral nerves. One of the main methods used to investigate the condition of this structures is an electroneiromyography and, as it part, the investigation of H-reflex. Studying of an H-reflex leads to understanding of the condition of conductivity of reflex curve including sensory and motoric fibers outside the spinal cord and its intraspinal part. Also it is possible to evaluate the excitability of spinal motoneurons using this method.

During the analysis of the results usually the latency of H-reflex, its amplitude, H reflex to M response threshold ratio, amplitude of maximum H-reflex to maximum M-response ratio, vibration H-reflex to control H-reflex and H-reflex recovery curves evaluates.

H-reflex latency is a more or less constant value, little dependable of an appendant circumstances (for example, it became longer on 0,5 - 1,0 ms depending to the rising of the duration of the irritating stimuli).

Unlike it the amplitude of H-reflex is a very changeable value, dependable of the condition of voluntary muscle activation, frequency of stimulation, accuracy of attachment of reference and stimulating electrodes, ground connection, condition of myograph, mass of subcutaneous tissue and a lot of other factors. (1)

Thus, the analyzing of H-reflex amplitude and its correlations with amplitude of M-response (which also liable to the lot of ill-wresting factors) must be performed with a certain caution.

Some reports (2, 3, 4) investigated parameters of H-reflex during different disorders of extrapyramidal system, including Parkinsonism syndrome.

We did an investigation that was going to analyze changes of H-reflex latency during the Parkinson's disease.

20 patients were studied, group of 10 patients with Parkinson's disease, age between 39 to 79 years old (average age 59,4 years old) - 7 females and 3 males, and control group including 10 patients - 5 females and 5 males, age between 18 to 56 (average 39,4 years old).

To the control group we choose neurologically healthy persons (2 patients) and neurological patients without signs of lesions of peripheral nerves (polineuropathy, radiculopathy) and spinal cord (8 persons). Choosing group members we excluded persons with: smoking, chronic alcohol intoxication, prolonged usage of any pharmacological medicaments, endocrinological pathology, hematological diseases, diseases with any metabolism shift, occupational diseases.
Latency of H-reflex in control group was 30,1 ms.
Group of patients with Parkinson's disease consist of, as it was said earlier, 10 members. An overwhelming majority (78%) of them had an III stage of a disease by Hoehn and Yahr classification. 22% had a II stage of the disease.

All of them received specific therapy, duration of treatment vary between 2 to 10 years. Following medicaments were used: piribedil (56% of cases), L-Dopa group: madopar (30 %), nacom (11%), midantan (22%).
For this group we excluded the same disutilities, as for the control group.
Latency of H-reflex in this group was 31,47.
In both groups H-reflex from m. gastrocnemius was analyzed.

	Average age, years	Average H-reflex latency, ms	Stimulation intensivity, ma
Control group	39,4	30,1	20
Disease group	59,4	31,47	20

Thus, difference in latency value in both groups is quite slight (1,37 ms), and for the both groups latency value it almost entirely conform the parameters of medical standards for ENMG.

According to this results we come to the conclusion that H-reflex latency, as its most stable and reliable characteristic, do not change substantially during Parkinson's disease.

References:

1) Komantsev V.N., Zabolotnih V.A. Methodical bases of clinical electroneiromyography.

2) Starikov V.S.
[The electrical excitability of the peripheral motor neuron in parkinsonism]
Zh Nevropatol Psikhiatr Im S S Korsakova. 1993;93(6):11-5

3) Sabbahi M, Etnyre B, Al-Jawayed IA, Hasson S, Jankovic J.
Methods of H-reflex evaluation in the early stages of Parkinson's disease.
J Clin Neurophysiol. 2002 Jan;

4) Sabbahi M, Etnyre B, Al-Jawayed I, Jankovic J.
H-reflex recovery curves differentiate essential tremor, Parkinson's disease, and the combination of essential tremor and Parkinson's disease. J Clin Neurophysiol. 2002 Jun;19(3):245-51.

5) Kushnir M, Klein C, Pollak L, Rabey JM. H reflex threshold in Parkinson's disease patients for different stimulus duration.
Parkinsonism Relat Disord. 2002 Dec;9(2):85-7.