Jen-Tse Chen

Reduction in hypothalamic 1H-MRS metabolite ratios in patients with cluster headache

Objective: To determine the 1H-MR spectroscopic (MRS) findings in the hypothalamus in patients with episodic cluster headache. Methods: 47 patients were recruited with episodic cluster headache (35 in cluster period and 12 in remission), 21 normal controls, and 16 patients with chronic migraine. The hypothalamic 1H-MRS metabolite ratio changes in patients with cluster headache were evaluated and compared with results in the normal controls as well as patients with chronic migraine. Seven patients in the cluster period group underwent a follow up hypothalamic MRS study five to six months after remission. Results: In patients with cluster headache, the hypothalamic N-acetylaspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios were similar between those in cluster period and in remission. As a group, both NAA/Cr and Cho/Cr levels were significantly lower in patients with cluster headache in comparison with either the control or chronic migraine groups. In those with a follow up MRS study, the levels of metabolite ratios did not differ between the cluster and remission periods. Conclusions: This study provides evidence of persistent biochemical change of the hypothalamus in patients with episodic cluster headache. Low levels of NAA/Cr and Cho/Cr suggest that cluster headache might be related to both neuronal dysfunction and changes in the membrane lipids in the hypothalamus.

Prolonged cortical relay time of long latency reflex and central motor conduction in patients with spinocerebellar ataxia type 6

OBJECTIVE Spinocerebellar ataxia type 6 (SCA6) is a neurodegenerative disorder characterized by a slowly progressive ataxia and dysarthria. Anatomically. SCA6 was said to affect only the cerebellum. However, ithasbeen argued that SCA6 may involve widespread regions of the brain. This study was designed to investigate the electrophysiological functions of the central nervous system in patients affected with SCA6. METHODS Nine patients with SCA6 and 10 normal, age-matched control subjects were included in the study. The motor evoked potentials, somatosensory evoked potentials, and long latency reflex (LLR) of the hand muscle were measured to evaluate the functions of the central nervous system. RESULTS Significantly delayed LLR, as well as prolonged cortical relay time (CRT) and central motor conduction time (CMCT) of the hand muscle, were noted in the patients with SCA6. CONCLUSIONS The prolongation of CMCT andCRT suggested that SCA6 disturbed the functions of the corticospinal tract and the transcortical polysynaptic pathways from the sensory to motorcortices. It seems likely that the CNS dysfunction caused by SCA6 is not limited to the structures that are anatomically abnormal. Furthermore, the prolongation of CMCT alone does not seem to suffice to differentiate between various types of autosomal dominant cerebellar ataxias. Molecular analysis is indispensable for the diagnosis of different genetic types of SCA.

Guillain–Barré syndrome coexisting with pericarditis or nephrotic syndrome after influenza vaccination

A 68-year-old woman and a 72-year-old man presented with distal weakness of the limbs and numbness following an influenza vaccination within 2 weeks. Moreover, Guillain-Barré syndrome (GBS) was diagnosed in two patients. Pericarditis was diagnosed in the first patient who also had precordial chest pain with referral to trapezius ridge, and nephrotic syndrome, was observed in the second patient who had leg edema and proteinuria. The relationship among GBS, pericarditis and nephrotic syndrome after an influenza vaccination is discussed.

Multimodal evoked potentials of Kennedy's disease

BACKGROUND Kennedys disease (KD) is an X-linked recessive polyglutamine disease. Traditionally, it is a lower motor neuron syndrome with additional features such as gynecomastia and tremor. Sensory symptoms are minimal if ever present. We used multimodal evoked potential (EPs) tests to study the distribution of the involvement of the disease. METHODS Visual, brainstem auditory, somatosensory and motor EPs were studied in six KD patients. All of them had typical presentations and had been proved genetically. RESULTS Abnormal findings were noted as follows: prolonged peak latencies of visual EPs, increased hearing threshold level, inconsistent brainstem auditory EPs, decreased amplitudes of cortical potentials of somatosensory EPs, and increased motor threshold to transcranial magnetic stimulation. CONCLUSIONS Our multimodal EP studies showed that KD involved multiple levels of the nervous system. It implies the widespread effects of the mutant androgen receptors.

Neurotoxicity of nitrous oxide: Multimodal evoked potentials in an abuser

Introduction. Nitrous oxide (N2O) damages the nervous system of chronic abusers. Multimodal evoked potentials (EPs) can help document the electrophysiological abnormalities of N2O abusers and its distribution in the nervous system. Case report. A 41-year-old male N2O abuser had used N2O (4–5 cans/per day, about 2000 ml/can) for more than 10 years. He complained of progressive motor clumsiness and distal paresthesia in the four limbs. Abnormal laboratory tests were megaloblastic red blood cells (102.3 fL, normal 80–94 fL) and serum vitamin B12 concentration of 143 pg/nL (normal 160–970 pg/nL). An MR image did not show significant findings in the brain but demonstrated conspicuous changes in the posterior and lateral columns at the C2-C7 level, in accordance with the anatomical lesions of the subacute combined degeneration of the spinal cord. In addition to sensori-motor axonal polyneuropathy, multimodal EPs showed abnormal visual EPs with prolonged peak latencies of P100, abnormal brainstem auditory EPs characterized by delayed wave V and difficulty in the recognition of waves I and III, abnormal somatosensory EPs with significant decreased peak amplitudes of cortical potentials bilaterally, and abnormal motor EPs to transcranial magnetic stimulation with prolonged central motor conduction time. Conclusion. Our studies document electrophysiological abnormalities that may be attributed to N2O and indicate that N2O may indirectly involve multiple levels of the nervous system.

Prolonged central motor conduction time of lower limb muscle in spinocerebellar ataxia 6.

We investigated the function of corticospinal tract in spinocerebellar ataxia 6 (SCA6) by measuring the central motor conduction time (CMCT). Motor evoked potentials (MEP) of tibialis anterior (TA) muscle were elicited by magnetic stimulation to motor cortex and spinal cord in 9 SCA6 patients and 10 normal height- and age-matched subjects. CMCT in lower limb of SCA6 patients (18.1+/-1.9 ms) was significantly prolonged than that of the normal subjects (15.0+/-1.0 ms) ((p < 0.001). The prolonged CMCT was well correlated with the duration of disease (p = 0.005), but MEP amplitudes and stimulation intensities were not significantly different. These results indicate that the corticospinal tract function is also impaired and correlate with the disease duration in SCA6.

Hypotension Due to Interaction Between Lisinopril and Tizanidine

OBJECTIVE To report a case in which significant hypotension occurred after initiation of tizanidine in a patient using the antihypertensive agent lisinopril. CASE SUMMARY A 48-year-old woman was admitted due to cerebral hemorrhage at the midbrain and pons, with extension to the fourth ventricle. Consciousness disturbance (Glasgow coma scale 4) with a decerebrate posture improved 5 days after stroke onset. As the BP was fairly high, antihypertensive agents, including lisinopril, were initiated. Three weeks later, the decerebrate rigidity and high BP remained, and tizanidine was initiated to see whether the decrease in muscle tone could facilitate hypertension control and motor recovery. However, the BP dropped dramatically within 2 hours after the first dose of tizanidine. The tizanidine and all of the antihypertensive medications were withdrawn. Tizanidine was used again after her BP had stabilized, but did not produce similar problems. DISCUSSION A similar event was reported in 2000. The reaction in our patient appeared after tizanidine initiation and improved after both lisinopril and tizanidine were discontinued. According to the Naranjo probability scale, this was classified as a possible drug interaction. This kind of reaction is seldom mentioned as occurring during co-administration with tizanidine. With its characteristics, tizanidine has the potential to compromise hemodynamic stability during concomitant angiotensin-converting enzyme inhibitor use. CONCLUSIONS Based upon the literature review, the hypotension in this patient was possibly due to the interaction between tizanidine and lisinopril.

Modulation of symptomatic palatal tremor by magnetic stimulation of the motor cortex.

OBJECTIVES Magnetic stimulation of the motor cortex can be used to determine the involvement of the cortex in rhythmic movement disorders. Symptomatic palatal tremor (SPT) is thought to come from a pacemaker that is relatively resistant to internal and external stimulation. In this study, we investigated the effect of magnetic stimulation of motor cortex on SPT. METHODS Five male patients, aged 67-79 years, with SPT after brain stem infarction or hemorrhage, all had a synchronous mouth angle twitch with the palatal movement. Electromyographic activity was recorded with a monopolar needle electrode from orbicularis oris. In experiment 1, transcranial magnetic stimulation (TMS) was delivered at 200% motor threshold (MT) to reset SPT. In experiment 2, the effect of TMS intensities was studied at 80-240% MT in two SPT patients. To determine the influence of the TMS, we used the resetting index (RI). RESULTS TMS reset the tremor in all 5 SPT patients at 200% MT with RIs of 0.86-0.96. The latency of the tremor reappearance after TMS was longer than the pre-stimulus tremor interval, and the intervals between the subsequent tremor bursts were also prolonged. The degree of tremor resetting was closely correlated with the magnetic stimulus intensity and the latency of the tremor reappearance after TMS. CONCLUSIONS Stimulation of the motor cortex may modulate the generator of SPT.

Cutaneous reflexes in patients with acute lacunar infarctions

Cutaneous reflex (CR) was measured in 15 patients with acute lacunar stroke and in 15 age- and sex-matched normal subjects. EMG activities were recorded from the first dorsal interosseous muscle with surface electrodes, rectified and averaged. Intensity of the stimulation on the index finger was four times the sensory threshold. Aided by audio- and visual-feedback monitoring, the subjects abducted the index finger. Side-to-side comparison was made on all the subjects. CR abnormalities were found in all of our patients. The early inhibitory (I1) and second excitatory (E2) components were attenuated in 11 of 15 patients. The I1-E2 interpeak amplitude (A2) was significantly reduced in all the patients. Prolonged latency of I1-E2 components was found to be pronounced in six of eight patients with sensory symptoms. Eight patients were followed up 1 month later. By that time, the abnormal CR had reversed to some degree in all of them. CR alternation was still present in two fully recovered patients. Our results implied a thalamic relay in the afferent limb of the CR. CR could be a valuable adjunct for assessing long tract dysfunction and monitoring functional recovery.

Brainstem Excitability is Increased in Subjects with Palmomental Reflex

BACKGROUND/PURPOSE The palmomental reflex (PMR) is a brief contraction of the mentalis muscles caused by a scratch over the thenar eminence, i.e. a brainstem reflex to afferents of upper limb. Using electrophysiologic methods, we studied the characteristics of brainstem excitability in PMR subjects. METHODS Ten healthy PMR subjects were included in the study. Brainstem excitability was assessed with electrical stimulation at the trigeminal nerve, median nerve, ulnar nerve, and sural nerve with recordings at the mentalis muscles. A comparison was made by the probability between the mechanical scratch and the electrical stimulation to evoke the visible muscle contraction of mentalis. RESULTS An electrical stimulus was able to elicit mentalis muscle responses (MMR(electrical)) in all the subjects if the stimulus was of sufficient strength. Using electrical stimulation, the median nerve at the wrist was the best site to evoke MMR(electrical). However, in PMR subjects, the probability of MMR(electrical) to median nerve stimulation was less than that of MMR(scratch), i.e. the clinical findings of PMR. Significantly lower thresholds and higher amplitudes were noted in PMR subjects only when the median nerve was stimulated. The onset latency did not show any difference between the two groups despite the stimulation sites. CONCLUSION The facial motor neurons to median nerve stimulation are more sensitive in PMR subjects. In healthy PMR subjects, this indicates that the excitability increases only in the specific neuronal circuits between the lower cervical spinal cord and the facial motor nucleus in the rostral medulla. MMR(electrical) is a physiologic phenomenon, and PMR is a sign of increased brainstem excitability.