A. Emre Öge

Concentric needle electrode for neuromuscular jitter analysis

We used a concentric needle electrode (CNE) with 2 kHZ low‐cut filter and a single fiber electrode (SFE) in the same subjects for neuromuscular jitter measurement in the extensor digitorum communis (EDC) and orbicularis oculi (OOc) muscles. At the same session, 20 jitter values were obtained from each subject with each electrode. For EDC (during voluntary contraction), mean jitter values with SFE and CNE were 23.4 ± 8 μs and 23.3 ± 8 μs in 10 normals; and 56.8 ± 28 μs and 57.4 ± 33 μs in 10 myasthenics. For OOc (during electrical stimulation), mean jitter values with SFE and CNE were 17.9 ± 5 μs and 16.3 ± 4 μs in 11 normal subjects, and 41.2 ± 29 μs and 36.7 ± 27 μs in 10 myasthenics. For both muscles, the numbers of individual abnormal jitter values with SFE and CNE were highly comparable. Both needles labeled the same patients as having “normal” or “abnormal” neuromuscular transmission. CNE may be an alternative to SFE in neuromuscular jitter analysis.

Excitability of facial nucleus and related brain-stem reflexes in hemifacial spasm, post-facial palsy synkinesis and facial myokymia

OBJECTIVE To compare the electrophysiological excitability characteristics of the facial nucleus and related structures in hemifacial spasm (HFS), post-facial palsy synkinesis (PFPS) and facial myokymia (FM). METHODS Facial F-waves, blink reflex recoveries and magnetically elicited silent periods (SP) were prospectively studied in 17 HFS, 17 PFPS, 8 FM cases and in 13 controls. Earlier unpublished observations on abnormal impulse transmission in 36 HFS and 29 PFPS cases were also included. RESULTS Enhanced F-waves were recorded on the symptomatic side in PFPS and HFS cases with a tendency to be more pronounced in PFPS. HFS and PFPS groups both showed an earlier blink reflex recovery, more prominent in PFPS patients, when stimulated and/or recorded on the symptomatic side. Unelicitable SPs were encountered after 24/39 stimulations in 5 patients with PFPS and rarely in HFS cases. Duration of elicitable SPs did not change remarkably. FM group had similar characteristics as normal controls in the 3 electrophysiological tests. Latencies of the lateral and synkinetic spread responses were significantly prolonged in the earlier PFPS group as compared to HFS. In two-point stimulation, both groups showed a greater latency shift in late responses, again more pronounced in PFPS. CONCLUSIONS PFPS and HFS cases had similar enhanced excitability patterns at the facial nucleus and related brain-stem structures, more marked on the symptomatic side and more obvious in the PFPS group. Findings elicited in the FM group were thought to be caused by asynchronous hyperactivity of facial motoneurons. SIGNIFICANCE In this comparative electrophysiological study, similar excitability patterns were found in HFS and PFPS groups, albeit with different intensities.

Electrophysiological findings in patients who received radiation therapy over the brachial plexus: a magnetic stimulation study

Clinical and electrophysiological findings of 47 asymptomatic females who received radiation therapy (RT) over their brachial plexus region are presented and compared with 8 radiation-induced brachial plexopathy (RBP) and 4 neoplastic brachial plexopathy (NBP) patients. In the asymptomatic group, abnormal findings were more frequent in patients whose post-RT period was longer than 1 year. Flexor carpi radialis H reflex was delayed or absent in 19 patients (52%) in this subgroup of asymptomatic cases, as compared to only 2 (18%) of the patients with post-RT periods of less than 1 year. Magnetic cervical nerve root stimulation was performed in 16 asymptomatic cases, with the conclusion that there was no significant difference between the irradiated and non-irradiated sides with regard to latencies, amplitudes and areas of the muscle responses. In spite of this, muscle response amplitudes and areas on both sides were significantly lower than those obtained from healthy controls. It was postulated that this finding resulted from hypoexcitability to magnetic stimulation produced by slight nerve root damage. Any part of the brachial plexus could be affected in RBP and NBP patients. Myokymic discharges were found at a high rate (87.5%) in RBP group. Cervical magnetic nerve root stimulation may have a diagnostic value in these patients in localizing the nerve lesion over the brachial plexus.

The use of botulinum toxin in localizing neuromyotonia to the terminal branches of the peripheral nerve.

In 2 patients with neuromyotonia, nerve blocks had no effect on the abnormal activity, while intramuscular injection of the botulinum toxin abolished the discharges in one and greatly diminished them in the other. Botulinum toxin thus helps to localize the origin of the neuromyotonic discharges to the terminal regions of the peripheral nerve in those cases where the more proximal portions cannot be held responsible.

Magnetic nerve root stimulation in two types of brachial plexus injury: Segmental demyelination and axonal degeneration

Magnetic cervical nerve root stimulation was performed in 9 patients with plexopathies secondary to suspension (SP) and in 12 cases with neurogenic thoracic outlet syndrome (NTOS). The findings were compared with those of the previously reported case groups: n‐hexane polyneuropathy (HPNP), inflammatory demyelinating polyneuropathy (IDP), and motor neuron disease (MND). Muscle responses elicited by magnetic stimulation had very high rates of amplitude and area loss in the neck–axilla segments of the 6 SP patients. This, along with the other electrophysiological findings, suggested the presence of segmentally demyelinating plexus lesions. In NTOS patients, magnetic stimulation findings were not significantly different from those of the controls. Neck–axilla segment amplitude and area reduction rates in SP and IDP patients were significantly higher than those found in NTOS, HPNP, and MND groups, implying that magnetic nerve root stimulation may have a role in the demonstration of segmentally demyelinating lesions involving proximal nerve segments.

Neuromuscular consequences of prolonged hunger strike: an electrophysiological study☆

OBJECTIVES The purpose of this study was to determine the electrophysiological consequences of neuromuscular and central nervous system involvement in a group of patients presented with the neurological complications of a long-term hunger strike (HS). METHODS Motor and sensory nerve conduction (NCV), F wave, somatosensory evoked potential (SEP) and motor evoked potential (MEP) studies were performed in 12 male and 3 female patients (mean age: 29.4) following HS. RESULTS All patients whose weight loss was 11-31 (mean: 22.8) kg after 69-day HS, had neurological findings consistent with Wernickes encephalopathy or Wernicke-Korsakoff syndrome. Abnormally prolonged latency and/or low amplitude sensory nerve action potentials were found in 7 patients. The amplitudes of compound muscle action potentials were significantly reduced in ulnar, median and tibial motor NCV studies as compared to the controls. F waves elicited by median nerve stimulation at wrist and muscle responses evoked by cervical and lumbar magnetic stimulation had significantly prolonged latencies. MEPs recorded from the lower extremities showed a slight prolongation in central conduction times. The cortical response latencies were prolonged in tibial SEPs. CONCLUSIONS The most prominent finding in this patient group was the low amplitude of CMAPs elicited in motor NCV studies which was concluded to be resulted from the reversible muscular changes. The other electrophysiological findings suggested that peripheral nerves and long central nervous system pathways were also mildly involved.

Excitability changes at brainstem and cortical levels in blind subjects.

OBJECTIVES This study was designed to search potential changes in trigemino-facial system in blind subjects by the use of relatively well-established electrophysiological methods. Excitability changes in the motor cortex were also investigated by transcranial magnetic stimulation studies (TMS) with the expectation of finding some abnormal interactions between the cortex and brainstem. METHODS Twenty blind (BS) and 13 control subjects (CoS) were included in the study. Blink reflex and its recovery with paired electrical stimulation were studied at 150, 200, 300, 400 and 500 ms interstimulus intervals (ISI). Facial F waves elicited by buccal branch stimulation were recorded from nasalis muscles. Motor cortex excitability with recordings from left first dorsal interosseus muscle was studied by using magnetically elicited silent periods and paired magnetic stimuli, subthreshold conditioning and suprathreshold test, given at ISIs of 2, 3, 4, 10, 12, 15 and 20 ms. RESULTS Blink reflex recovery was significantly reduced in BS group comparing to CoS at 400 and 500 ms ISIs. This difference between the groups was more prominent for the responses evoked by the initial stimulation side and faded away with stimulations on the contralateral side. Facial F wave amplitudes and F/M amplitude ratios were higher in BS group. In TMS studies, the early inhibitions at 2 and 4 ms were found to be significantly less in BS as compared to that of CoS. CONCLUSIONS The reduced blink reflex recovery and its fast restoration with continuing stimulation might be explained by conditioning and extinction processes which have been shown to be mainly carried out by cerebellar-brainstem pathways. Our TMS studies showed reduced intracortical inhibition in the motor cortices of BS cases and facial F wave studies revealed the possible effect of this altered excitability on the facial motor nuclei. SIGNIFICANCE Firing probabilities of facial motor neurons in BS are probably determined by the equilibrium between the low-set excitability of blink reflex interneurons and the enhanced excitability brought on by the descending motor pathways.

Motor unit number estimation in facial paralysis.

The value of motor unit number estimation (MUNE) in determining the prognosis of acute peripheral facial paralysis (PFP) was evaluated in 89 patients with PFP on days 6, 8, 11, 14, 20, and 30 of PFP and repeated once per month until complete recovery or the end of the first year. The symptomatic/asymptomatic side ratios of the compound muscle action potential (CMAP) amplitudes recorded from nasalis muscles and MUNEs studied using the incremental method by recording from the same muscle were assessed with regard to three outcome groups (Group I, complete recovery; Group II, mild dysfunction; Group III, moderate–moderately severe dysfunction). CMAP and MUNE ratios were parallel to each other in all patient groups throughout the observation period with lower values in the more severe groups. However, CMAP amplitude loss was significantly greater than the MUNE loss in the first 3 weeks of PFP. The MUNE method is not superior to CMAP size in determining prognosis in PFP. However, the significant disparity between the CMAP and MUNE ratios in the early period may have some physiological relevance with regard to the pathophysiology of the Wallerian degeneration process and deserves further research into its potential sources. Muscle Nerve 38: 1420–1428, 2008

Diagnostic use of dermatomal somatosensory-evoked potentials in spinal disorders: Case series

Abstract Objective/Context Dermatomal somatosensory-evoked potentials (dSEPs) may be valuable for diagnostic purposes in selected cases with spinal disorders. Design Reports on cases with successful use of dSEPs. Findings Cases 1 and 2 had lesions causing multiple root involvement (upper to middle lumbar region in Case 1 and lower sacral region in Case 2). Cystic lesions in both cases seemed to compress more than one nerve root, and stimulation at the center of the involved dermatomes in dSEPs helped to reveal the functional abnormality. Cases 3 and 4 had lesions involving the spinal cord with or without nerve root impairment. In Case 3, an magnetic resonance imaging (MRI)-verified lesion seemed to occupy a considerable volume of the lower spinal cord, causing only very restricted clinical sensory and motor signs. In Case 4, a cervical MRI showed a small well-circumscribed intramedullary lesion at right C2 level. All neurophysiological investigations were normal in the latter two patients (motor, tibial, and median somatosensory-evoked potentials in Case 3, and electromyography in both) except for the dSEPs. Conclusions Objectifying the presence and degree of sensory involvement in spinal disorders may be helpful for establishing diagnoses and in therapeutic decision-making. Valuable information could be provided by dSEPs in selected patients with multiple root or spinal cord involvement.

A Novel Electrophysiological Method in the Diagnosis of Pudendal Neuropathy: Position-related Changes in Pudendal Sensory Evoked Potentials

OBJECTIVE To examine the diagnostic value of pudendal somatosensory evoked potentials (SEPs) in pudendal nerve entrapment (PNE) neuropathy by stimulating the 2 sides separately after provocation by a standard sitting position. Routine pudendal SEPs performed in the supine position with bilateral simultaneous stimulation may fail to show the abnormality because the complaints of PNE appear or worsen in the sitting position. METHODS Forty-nine patients with PNE and 16 controls were included. SEP recordings were performed by stimulating the dorsal nerve of penis or clitoris on either side. The recordings were performed at the initial supine position, at the beginning and end of the provocation by sitting position, and at the second supine position. RESULTS Amplitude loss in the SEP responses after prolonged sitting was significantly more pronounced on the symptomatic sides of the patients. Approximately 45% decrease in the SEP amplitude or an amplitude value less than 1.5 µV at the end of sitting are the parameters to be used with high selectivity. CONCLUSION The dynamic pudendal SEP study described herein seems to be more helpful in PNE diagnosis than in conventional SEPs.