Neurophysiological investigations in patients with head tremor

Abstract

We studied 30 patients whose primary complaint was head tremor in an attempt to characterize neurophysiological aspects of their abnormal movement. Based on family medical history and physical examination, 23 patients had definite or probable essential tremor (essential head tremor, EHT). The remaining seven had mild dystonic signs accompanying their head tremor (head tremor plus dystonic signs, HT + DS). We recorded head movement and the electromyographic (EMG) activity of the sternomastoid and splenius capitis muscles, determined the spontaneous blinking rate, and measured the excitability recovery curve of the blink reflex and of the masseteric inhibitory reflex. All patients had tremor bursts at a frequency ranging between 3 and 9 Hz in at least one of the muscles examined. The predominant pattern seen when patients were sitting relaxed and facing forward was that of synchronized EMG bursts in both splenius capitis muscles. Maintenance of extreme head postures demonstrated two types of additional abnormalities: type 1 (enhancement of tremor), which was observed in 11 patients (47.8%) with EHT and in two (28.5%) with HT + DS; and type 2 (activation of neck muscles not required for maintenance of the posture), which was observed in two patients (8.7%) with EHT and in five (71.5%) with HT + DS (chi 2 = 26.4; p < 0.001). Mean blinking rate per minute was 24.9 +/- 14.6 in patients with EHT and 42.3 +/- 10.5 in patients with HT + DS (paired t test, p = 0.001). The blink reflex and masseteric inhibitory reflex excitability recovery curves showed an abnormal interneuronal excitability enhancement in seven (30.4%) of the 23 patients with EHT and in two (28.5%) of the seven with HT + DS (chi 2 = 3.1; p > 0.05). Abnormal patterns of EMG activity of the neck muscles correlated well with the presence of mild dystonic signs. However, the analysis of brainstem interneuronal excitability did not enable recognition of those patients with head tremor who could potentially develop cervical dystonia. The enhancement of brainstem interneuronal excitability found in approximately 30% of patients with head tremor could be related to plastic changes triggered by increased activity of the cranial muscles.

Quantification of sensory trick impact on tremor amplitude and frequency in 60 patients with head tremor

“…The mean peak tremor frequency in our patients with TCD and DHT was slightly below 5 Hz and with EHT slightly above 5 Hz, which is in accordance with results from previously published studies of dystonic or essential head tremors. 6,7,[10][11][12] Our findings of a significant reduction of head tremor magnitude during sensory trick maneuvers in patients with clear-cut TCD are in accordance with clinical observations 1 and polymyographic findings, 7 which showed suppression of dystonic neck muscle activity, including tremor bursts, during a geste maneuver. Individual tremor-suppressing maneuvers in patients with TCD are clinically comparable to trick maneuvers observed in patients with other forms of CD (pure tonic, phasic, or mixed dystonic muscle activities).…”

“…Cleeves et al 16 termed the occurrence of dystonia and tremor in the same body part "dystonic tremor," even in those patients in whom dystonia could only be recognized on electrophysiological assessment, for example, an impaired reciprocal inhibition in poly-EMG recordings. Valls-Solé et al 12 found significantly more abnormal postural EMG activation patterns in patients with head tremor and associated mild dystonic signs than in patients with EHT. In addition to an impaired reciprocal inhibition, none of the patients with the diagnosis of DHT had responded to drugs that are known to ameliorate EHT or had a positive family history of postural hand tremor.…”

Lateralization of the P22/N30 precentral cortical component of the median nerve somatosensory evoked potentials is different in patients with a tonic or tremulous form of cervical dystonia

“…None of these antagonistic muscles fulfilled the criteria for being dystonic muscles. This observation was already published in other studies examining patients with dystonic head tremor 23,26,27,46,47 and probably indicates that these muscles are only secondarily involved in the dystonic dyskinesia. Indeed, dystonic head tremor usually starts as a slight rotation of the head with later development of tremor.…”

“…The recordings were further studied regarding the frequency of tremor, irregularity of tremor pattern, duration of bursts (100-500 ms), and synchronization of the agonist and antagonist muscle activity, and served in these patients also as a tool in the characterization of the type of dystonic head tremor. In all 20 patients polymyographic characteristics of head tremor fulfilled the published criteria for dystonic tremor, 22,23,[26][27][28] that is, the presence of co-contractions, irregular tremor pattern, and duration of bursts. The recordings excluded the possibility that the essential head tremor might be mistakenly diagnosed as a tremulous form of torticollis in our patients.…”

Head tremor in Parkinson's disease

“…Movements of both upper eyelids were measured with the magnetic search coil technique 8 (for detailed infor-…”