Tetsuji Fujiwara

Intramedullary spinal cysticercosis.

Intramedullary cysticercosis of the spinal cord is rare; there have been only 26 previous cases. We describe a patient with low back pain, paraparesis, lumbosacral sensory loss, and signs of meningeal irritation. The clinical diagnosis was spinal cord tumor, but at surgery there was a cysticercus cyst w.ithin the lumbosacral cord. Careful search did not reveal the parasite in any other part of the body. This is the first case of spinal cysticercosis reported in Japan.

Excitability of the spinal motor neuron pool and F-waves during isometric ipsilateral and contralateral contraction

We recorded the F-waves from opponens pollicis muscle during isometric contraction following stimulation of the right median nerve in male and female subjects. The F-waves were recorded in the following five conditions: 25, 50, 75 and 100% isometric contraction of the right opponens pollicis muscle, and 25% isometric contraction with simultaneous 100% contralateral contraction. The F-waves in 20 trials were analysed with respect to persistence, F/M amplitude ratio, latency, duration and phase of the wave. Persistence and the F/M amplitude ratio increased with increasing contraction strength; however, latency, duration and phase were unchanged. There was no significant difference between 100% contralateral contraction and contralateral relaxation on F-waves recorded from ipsilateral muscle, for all parameters. These results suggest that excitability of anterior horn cells in spinal cord increases with isometric contraction, but contralateral contraction has no such effect on excitability.

Characteristics of the F-Wave and H-Reflex in Patients with Cerebrovascular Diseases: A New Method to Evaluate Neurological Findings and Effects of Continuous Stretching of the Affected Arm

The F-wave is a result of the backfire of α-motoneurons following an antidromic inva‐ sion of propagated impulses across the axon hillock (Kimura, 1974). Its occurrence reflects excitability changes in the spinal motor neurons, as reported in patients with spasticity (Odusote & Eisen, 1979) and in healthy subjects with isometric contraction (Suzuki, Fujiwara & Takeda, 1993). In our previous study that investigated the nervous system of hemiplegic patients, excitability of spinal neural function was evaluated using F-wave data of patients with cerebrovascular disease (CVD) (Suzuki, Fujiwara & Takeda, 1993). We also reported that the persistence and amplitude ratio of F/M in patients with CVD were affected by the grade of muscle tonus, tendon reflex, or voluntary movement. Persistence reportedly depends on the number of neuromuscular units activated, while the ampli‐ tude ratio of F/M depends on their excitability (Eisen and Odusote, 1979). Therefore, we concluded that F-wave measurement was an effective neurological test for evaluating muscle tonus and voluntary movements.

Clinical Application of Silent Period for the Evaluation of Neuro-Muscular Function in the Field of the Sports Medicine and Rehabilitation

A transient suppression of muscle activation was produced by electric stimulation to the innervating nerve during continued effort. This period of electrical inactivity, designated the mixed nerve silent period, results from several physiologic mechanisms (Kimura, 2001). On the other hand, the silent period during tonic muscle contraction demonstrated on electromyography is due to the rapid voluntary movement during tonic and mild muscle contraction (Ikai, 1955) and is elicited by cutaneous electrical stimulation of supplying nerve during muscle contraction (Higgins & Lieberman, 1968). In many previous studies about silent period, it was generally classified into three categories: (1) the quiet period of bursting wave activity on electromyography, recorded before the rapid motion in response to visual, auditory, light and/or sound stimulation (Yabe, 1976); (2) a transient suppression of muscle activation following electric stimulation of the mixed nerve innervating that muscle during continued effort (Kimura, 2001); (3) a pause of the muscle activity following the motor potential elicited by cortical magnetic stimulation during voluntary target muscle contraction (Calancie et al, 1987). In this study, we used the second category, according to which the silent period consists of several waves, including M wave, F wave and Long Latency Reflex (LLR). The silent period in this article, which classified in the second category, is the duration of the inhibitory period of muscle contraction detected on surface electromyography, which is due to electrical stimulation at the innervating nerve during tonic muscle contraction (Figure 1). We have considered that the silent period of lower extremity is the total circuit time from the peripheral nerve stimulus point to the central nervous system (i.e., brainstem or motor cortex), because the M wave, F wave and LLR are included in the silent period on evoked electromyography. M wave is affected by the conductive condition of peripheral nerve and the muscle state (i.e. rest or contraction, length, volume and so on) (Fuglevand et al, 1993, Cupido et al, 1992, Behm & St-Pierre, 1997). F wave is influenced by the excitability of the spinal motor neuron function (Suzuki et al, 1993). LLR in the lower extremities is affected by

HISTOPATHOLOGICAL STUDIES OF THE ARACHNOID AND RADICULAR NERVES IN VARIOUS DISEASES

Since the classical work of KEY and RETZIUS~) on the leptomeninges of the central nervous system appeared in 1876, various kinds of papers have been published in this field up to the present time, and it appears that there are few new data, anatomical as well as pathological, to add. Recently, Prof. M. MAEKAWA and his co-workers observed the relation between the pathological changes of the spinal arachnoid and psychosomatic diseases, and have reported a number of investigations in this field. From this point of view, the spinal arachnoid in various kinds of diseases has been examined and a clinico-pathological correlation has been investigated in full detail. The present paper describes several pathological findings dealing with the arachnoid and the radicular nerves in the spinal cord, and discusses the pathogenesis of these findings. Forty cases without any particular nervous diseases were chosen from among the patients who were admitted to, as well as those who died at the MAEKAWA clinic, and who were well-known in clinical pictures and laboratory findings.