Michinori Yokomizo

Carotid artery resection for head and neck cancer

BACKGROUND Carotid artery resection has been shown to yield a chance of cure in patients with advanced head and neck carcinoma involving the carotid artery. However, the criteria for the identification of those who are vulnerable to neurologic injury after resection have not been established. Interposition grafting may minimize the risk of neurologic morbidity, although it is technically difficult when there is involvement of the internal carotid artery close to the skull base. METHODS We studied 24 patients with head and neck tumor involvement of the carotid artery. We performed carotid artery resection in 16 of them, including 10 in whom the carotid artery was reconstructed with interposition grafts covered with muscle flaps. When it was thought that the reconstruction would be difficult, positron emission tomography was performed during balloon test occlusion of the internal carotid artery to assess the adequacy of hemispheric collateral blood flow before carotid resection. In one patient with interposition graft, carotid rupture occurred as a result of wound infection, but none of the other patients experienced perioperative death, persistent hemiplegia, or delayed stroke. RESULTS Twelve patients have survived longer than 8 months, and seven (43.8%) were alive without disease at 12 months after resection, whereas all four patients who could not be treated operatively died within 8 months as a result of local primary tumors. CONCLUSIONS Carotid artery resection is the only therapy offering any potential for cure or palliation. Positron emission tomography is a rapid quantitative means of determining the cerebral blood flow, particularly when resection is planned without reconstruction.

Analysis of Gait in Patients with Peripheral Vestibular Disorders

Analysis of gait in patients with acute unilateral peripheral vestibular disorders was performed using foot switches and electromyography, with the aid of a telemetry system. Among the eight parameters set for the analysis, the occurrence rate of abnormality in the coefficient of variation (CV) was the highest (78%) for the time from heel strike to forefoot strike, followed by that of the location of maximum monophasic contraction of the gastrocnemius during stance, swing and stance. No significant laterality concerning the abnormally increased CV value in those parameters was found except for swing of the foot contralateral to the lesion side. The CV value of each parameter was significantly increased by removing visual cues, suggesting the importance of visual input for steady locomotion. No significant change in CV values of double support was obtained during the acute stage of vestibular neuronitis, indicating that weight transfer from one leg to the other could be smooth even though some difficulty was expected. Abnormal parameters at an acute stage returned to normal limits at recovery stage. The physiological background of the obtained results is discussed.

Characteristics of Human Gait Related Variables in Association with Vestibular System Disorders

Gait analysis was performed in patients with vestibular system disorders, using foot switches and electromyography. They were divided into three groups: 11 cases with vestibular neuronitis (VN), 10 cases with large acoustic neuroma (LAN) who had central lesion evidenced by neurotological examinations, and 10 cases with olivopontocerebellar atrophy (OPCA). A total of 14 healthy adults served as controls. Results showed that time from heel strike to forefoot strike was the most sensitive variable to indicate gait abnormality but had no specificity. As for the variables of stance, swing, and time to reach the initial peak of the tibialis anteriors activity from forefoot off, occurrence rate of abnormality was high in the OPCA group, followed by the LAN and VN groups. Concerning the double support period which is related with body weight transfer from one leg to the other, the LAN and OPCA groups showed higher occurrence rate of abnormality than the VN group. These differences among the three groups could reflect different effects to the gait control systems caused by lesion.

Effect of unilateral section of cervical afferent nerve upon optokinetic response and vestibular nystagmus induced by sinusoidal rotation in guinea pigs

An experiment was carried out in guinea pigs to clarify the effect of unilateral section of cervical afferent nerve (C1-C3) upon optokinetic nystagmus and vestibular nystagmus induced by sinusoidal rotation. To produce optokinetic nystagmus and optokinetic after-nystagmus, a random dot pattern was utilized as visual stimulation at a speed of 30 degrees/s. As for vestibular nystagmus, sinusoidal rotation at a frequency of 0.1 Hz with an amplitude of 120 degrees was used. Results showed that for about a week after the surgical section of the C1-C3 nerves, directional preponderance of the vestibular nystagmus was found toward the lesion side, whereas no significant change was obtained in optokinetic nystagmus and optokinetic after nystagmus. This asymmetric change of the vestibular nystagmus was compensated for within a week or two. Thus. unilateral section of the cervical afferent nerve produced only a temporary effect on the vestibulo-ocular reflex but it had no significant effect on the optokinetic response.

Comparative Study on Gait Abnormality in Patients with Vestibular Neuronitis and Patients with Large Acoustic Neuroma

A comparative study on gait analysis comprising 11 patients with vestibular neuronitis and 10 patients with large acoustic neuroma was undertaken by the use of foot switches and electromyography. Central disorders in the neuroma group were evidenced by neurotological examinations. Fourteen healthy adults served as controls. Variables employed for the analysis were time from heel strike to forefoot strike (HA-I), time from heel off to forefoot off (HA-II) as well as duration of stance, swing and double supports (DS), location of maximum contraction of the gastrocnemius during stance, and location of the first and second peak of muscle contraction of the tibialis anterior from early swing phase (TA-off) to early stance phase (TA-on). The occurrence rate of abnormality of HA-I was the highest in both groups and most of the variables showed a higher rate in the large acoustic neuroma cases. In addition, a significantly higher CV value was obtained in HA-II of the lesion sides foot in the AN group. These changes could reflect the pathophysiological difference in the gait control systems between the two groups.