Investigation of the Blink reflex in tension type headache

Aida A.Yakupova, Maksum F.Ismagilov, Radik A.Yakupov Department of neurology.

State Medical University
Kazan, Russia The adequate diagnosis and treatment of tension type headache is an important problem of modern neurology. Meanwhile, the clinical and instrumental methods used routinely can not estimate the degree of pathological process and its dynamics objectively, because they do not reflect completely the main pathogenetic mechanisms of tension type headache, specifically, on the level of the brainstem functional systems in their interaction with the suprasegmental structures, which give the facilitating and inhibiting effects on this level. The purpose of the present work was to investigate the reflex excitability of the brainstem segmental systems in tension type headache on the basis of the blink reflex parameters. Materials&Methods: 49 patients (41 females, 8 males, age 22-52 y.o.) with the tension headache syndrome were examined. Diagnosis was performed on the basis of clinical features and electromyographic investigation of bioelectrical activity. The control group consisted of 20 healthy subjects which did not differ statistically from the experimental group by age and sex.  The investigations were conducted before and after the course of treatment which included medications and methods of acupuncture therapy. Methods of investigation included: clinical neurological examination; personal assesment of pain with the use of the visual — analogous scale (from 1 to 10 points); neuropsychological testing by MMPI; electromyography of the scalp and neck muscles; the blink reflex was recorded from the orbicularic oculi muscle. The supraorbital nerve was electrically stimulated (frequency 0,1 Hz, pulse duration 1 ms, pulse amplitude 5 — 7 mA); The reflex response consists of two temporally separate components: an early (constant) R1 and a late (variable) R2 components. The R1 is evoked at the same side of stimulation, whereas the R2 is recorded bilaterally with unilateral stimulation. The reflex arc of the blink reflex includes the afferents of the upper branch of the trigeminal nerve, the efferents of the facial nerve, as well as, the brainstem nuclei of these cranial nerves. The following parameters of the blink reflex were analysed: R1 and R2 thresholds, R1 latency, R2 latency, R2 duration, R1 amplitude, average R2 amplitude Results: Initially, in acute stage of headache before treatment, the following results were obtained: usually, the headache syndrome was characterized as monotonous, bilateral with localization in the fronto-temporal, parieto-occipital areas or as generalizing; bioelectrical activity for the frontal part of the epicranial muscle was recorded bilaterally without statistically significant difference of both sides in average 45,2±12,1mV; psychological status could be determined as a depressive-hypochondriac syndrome or anxious-hypochondriac syndrome on the background of the actual personal accentuations with the prevalence of anxious-hypochondriac type and tendency to the difficulty for interpersonal contacts; investigation of the BR revealed the statistically significant changes for the following parameters: the bilaterally decrease of the R1 threshold and the R2 threshold, the increase of the R1 amplitude and the average R2 amplitude, as well as, the R2 latency shortening and the R2 duration lengthening. correlation between the different parameters of the blink reflex were revealed, specifically, the direct connection of the R2 latency with the R2 threshold, the inverse connection between the R2 latency and its duration and the R2 latency; correlation between the personal assessment of pain, the blink reflex parameters and psychoemotional status were found, specifically, the direct connection with the R2 duration, the anxiety-depression scale of MMPI, the inverse connection with the R2 latency, the R2 threshold and the hypomania scale of MMPI. In dynamics, after the treatment, the regression of the clinical symptomatology was observed, specifically, the personal assessment of pain according to data of the visual-analogous scale, relief of the main psychoemotional syndromes. At the same time, despite the tendency to normalisation, the blink reflex parameters showed the statistically significant difference in comparison with the healthy persons. Conclusions: So, the results of the performed investigation revealed the rise of the brainstem reflex excitability in tension type headache. The findings characterized objectively the insufficiency of the intrasegmental inhibitory mechanisms, probably, because of the actual facilitating effects from the suprasegmental systems, especially, of the lymbico-reticular complex. It depends, on the one hand, on the decompensative action of the exogenic stress factors, on the other hand, on the constitutional peculiarities of its functioning. The remaining reflex disturbances during the headache remission give evidence in this direction. The brainstem hyporeflex activity is one of the final pathogenetic links in realization of the prolonged tonic spasm of the pericranial muscles in tension type headache. 1. The excitability rise of the brainstem neuronal systems, which participate in realization of the blink reflex, is found for patients with tension type headache. 2. The level of the brainstem reflex excitability is one of the pathogenetic factors for tension type headache.

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