Modulation of the excitatory phase following the cutaneous silent period by vibration.

INTRODUCTION: The post-inhibition excitatory phase (E3) of the cutaneous silent period (CSP) is attributed to the resynchronization of motoneuron activity following the inhibitory period but there is also evidence that a somatosensory startle reflex may contribute to this phase. We hypothesized that the startle reflex component contained in E3 will decrease during vibration. METHODS: Sixteen healthy individuals were included in the study. CSP was recorded from slightly contracted right thenar muscles after painful index finger stimulation, before, during, and immediately after vibration. The values of the percentage change of E3 relative to pre-stimulus baseline (E3%) were compared before, during, and after vibration for each individual. RESULTS: There was a reduction in E3% during vibration and the values returned to normal immediately after vibration (153.1 ± 43.5%, 115.2 ± 30.2%, 154.9 ± 68.2%, respectively; p = 0.030). DISCUSSION: E3 is reduced during vibration in healthy individuals, presumably due to suppression of a reflex component, which is superimposed upon the known resynchronization of motoneurons.

Mentalis muscle related reflexes.

The mentalis muscle (MM) arises from the incisive fossa of the mandible, raises and protrudes the lower lip. Here, we aim to characterize responses obtained from MM by supraorbital and median electrical as well as auditory stimuli in a group of 16 healthy volunteers who did not have clinical palmomental reflex. Reflex activities were recorded from the MM and orbicularis oculi (O.oc) after supraorbital and median electrical as well as auditory stimuli. Response rates over MM were consistent after each stimulus, however, mean latencies of MM response were longer than O.oc responses by all stimulation modalities. Shapes and amplitudes of responses from O.oc and MM were similar. Based on our findings, we may say that MM motoneurons have connections with trigeminal, vestibulocochlear and lemniscal pathways similar to other facial muscles and electrophysiological recording of MM responses after electrical and auditory stimulation is possible in healthy subjects.

Auditory-evoked masseter inhibitory reflex.

We aimed to investigate auditory-evoked masseter inhibitory reflex and discuss possible auditory-trigeminal pathways in brainstem. Our study population consisted of 21 healthy volunteers (age-matched 7 males and 14 females). Bilateral electrical blink reflex (BR), auditory blink reflexes (ABR) and electrical MIR (MIR) were studied. After obtaining normal potentials, auditory MIR (AMIR) was studied. Electrical blink reflexes had two components as R1 and R2, and ABR had one evoked potential in all volunteers. There was no significant difference between gender, nor between right- and left-sided BR and ABR. The mean latency of ABR responses were shorter than latencies of R2 phase of BR (p=0.013 for left-sided responses, p=0.035 for right-sided responses). Electrical stimulation revealed two suppression periods (SP1 and SP2) in MIR responses bilaterally in all volunteers. Auditory stimulation evoked typical two suppression periods only in 11 subjects (5 males, 6 females). The mean latency of SP1 component of AMIR was significantly longer than those of MIR bilaterally in both males and females, while the SP2 component had a shorter onset. The durations of SP1, SP2 and total SP were always shorter than those obtained in MIR with smaller degree of suppressions. None of the MIR or AMIR responses showed significance difference between sexes. We assume that auditory-evoked MIR might share the similar interneurons as with other electrical or nociceptive stimulation, which connects cochlear-trigeminal neurons via pontine reticular system to premotor area for masseter muscle.

What happens in the other eye? Blink reflex alterations in contralateral side after facial palsy.

Alterations in blink reflex excitability may occur in the contralateral side (CLS) and in the symptomatic side after peripheral facial palsy (PFP). In this study, the alterations of blink reflex in CLS were evaluated in cases with PFP who showed "three different types" of recovery. For this purpose, the R2 response area and recovery curve of the blink reflex were evaluated. The study included 51 patients suffering from PFP and 20 age- and sex-matched healthy controls. Cases with PFP were divided into three groups: patients with PFP with partially cured and accompanied by synkinesis (postfacial syndrome), patients with PFP with residual weakness, and patients who suffered from recurrent PFP. All three groups' R2 values of CLS were compared with the values of controls and patients who had synkinesis. The CLS of all three groups' R2 area values were found to be significantly higher when compared with controls. These values were found to be highest in patients who suffered from recurrent PFP. Hyperexcitability occurs in CLS after PFP and this is highest in patients who suffer from recurrent PFP. It suggested that the contralateral reorganization caused by peripheral nerve damage correlates with the severity of the lesion and the recurrence of axon damage enhances the excitability of the reflex cycle, which affects the contralateral facial nucleus.

The cutaneous silent period in diabetes mellitus.

The cutaneous silent period (CSP) may be useful as a method for the evaluation of smaller and unmyelinated fiber dysfunctions. CSP refers to the brief interruption in voluntary contraction that follows strong electrical stimulation of a cutaneous nerve. The aim the present study is to establish whether CSP can be instrumental in the determination of diabetic neuropathy. The nerve conduction studies and CSP evaluations were both used in patients with Diabetes Mellitus and control group. All patients were given clinical neurological examinations for the determination of small-fiber neuropathy (SFN). The CSP values for patients with SFN were compared with values of those without SFN. The nerve conduction velocities had changed unfavorably in diabetic patients. No median nerve CSP reponse could be obtained in two of the diabetic patients. CSP latency (84.6+/-14.0) in diabetics was longer than controls (76.2+/-13.1) (p=0.018). The duration of CSP was similar for the two groups (p=0.46). The CSP latency showed a correlation with routine nerve conduction studies. While the CSP latencies (86.7+/-15.8) of patients who were clinically diagnosed with SFN were similar to the latencies (81.3+/-10.4) of patients without SFN (p=0.606), the duration of CSP (44.6+/-13.7) in patients with SFN was shorter than the duration (55.3+/-12.2) in patients without SFN (p=0.012). These results indicate that even though the CSP does not provide any advantage over routine electrodiagnostic studies in determining diabetic neuropathy, still it may be a useful method for the early detection of diabetic SFN.

Traumatic peripheral nerve injuries: demographic and electrophysiologic findings of 802 patients from a developing country.

OBJECTIVE: To study a series of patients with traumatic peripheral nerve injury during the past 10 years in Cerrahpasa Medical Faculty/Istanbul/Turkey. METHODS: The chart review of 802 patients was evaluated and we explored the type(s) and cause(s) of injury, and electromyographic findings. The study included 171 children and 631 adults and we excluded the patients who suffered from injuries due to the Marmara earthquakes that occurred in 1999. RESULTS: Injury was most common in the upper extremities in both children (78.36%) and adults (63.54%). The common causes of nerve injury in children were as follows: obstetric lesions (46.78%), iatrogenic lesions (16.95%), traffic accidents (15.7%), and sharp lacerations (12.8%), whereas the commonest cause of nerve injury in adults was due to sharp lacerations (27.57%), followed by iatrogenic lesions (25.67%), and traffic accidents (23.77%). The most commonly injured nerves were the brachial plexus and ulnar nerve in children and adults, respectively. Electromyography demonstrated that complete nerve injury predominated in both groups. CONCLUSIONS: If preventive measures are taken into consideration satisfactorily, the incidence of disabling peripheral nerve injury may decrease, as such injuries are often treatable.

Electrophysiologic evaluation of peripheral nerve injuries in children following the Marmara earthquake.

The aim of this study was to investigate the clinical, demographic, and electromyographic (EMG) characteristics of 12 earthquake victims in the pediatric age group and to compare the findings with those of the adult group. Following the 1999 Marmara earthquake, 75 subjects with suspected peripheral nerve injury were referred to our EMG laboratory for evaluation. In the pediatric age group, five patients had a history of short-term temporary trauma and seven had a history of being trapped under the debris for 4 to 10 hours and sustaining long-term trauma. Five patients had developed compartment syndrome and one had developed crush syndrome. The EMG examinations revealed peripheral nerve injury findings in all patients. The brachial plexus was damaged in 2 patients, and 19 peripheral nerves were damaged in 10 patients. Peroneal and posterior tibial nerves were predominantly affected. Regeneration was detected in all of the patients with brachial plexus damage at a mean follow-up of 3.5 months and in 62.5% of patients with peripheral nerve damage at a mean follow-up of 7.7 months. Being buried under the debris, compartment syndrome, peripheral nerve injuries in the lower extremities, and total axonal damage in the first EMG examinations were found to be higher in the pediatric age group. Regeneration findings were found at similar rates in both groups, with the brachial plexus being the most favorable. When it is considered that the regeneration process lasts 15 to 18 months and EMG findings mostly show pathologies in the form of neuropraxia and axonotmesis, we think that the prognosis of our patients will be good.

1999 Marmara earthquake; peripheral nerve injuries--electrophysiologic evaluation.

This study evaluated the clinical, demographic and electromyographic (EMG) findings of 75 patients referred to our EMG laboratory with the preliminary diagnosis of peripheral nerve injury (PNI) during the 1999 Marmara earthquake. Forty-two patients had single and 33 had serial EMGs. Seventy-nine percent of the patients were found to have PNI. Eighty-six percent of these had PNI of the extremities and 23.7% had brachial plexus injury. PNI were detected in the upper extremities in 39% of patients, in the lower extremities in 47.5% of patients and in both extremities in 13.5% of patients. It was observed that brachial plexus degeneration was at a higher rate in patients with compartment and crush syndromes (35.70% and 42.9%) and peripheral nerve (PN) degeneration was higher in patients remaining under the debris (37%). In control EMG examinations, regeneration findings were observed at a rate of 79.2% in the upper extremities and 55.3% in the lower extremities (mean 64.5%) in the patients with PNI of the extremities and 90.9% in the patients with brachial plexus injury. In conclusion, after a mean EMG follow-up of 4 months in 75 earthquake victims a reasonably high level of regeneration findings shows that prognosis will be good in the majority of patients.

Motor unit potential analysis in the cases with hemifacial spasm and postparalytic facial hyperactivity.

This study seeks to find an answer to whether the damage caused by the focal demyelinated focus in hemifacial spasm (HFS) causes a deviation from normal in MUP's. The study evaluated MUP parameters of orbicularis oculi (o.oc) and orbicularis oris (o.or) muscles in the total of 76 cases, 41 of whom had a history of peripheral facial paralysis (PFP) and postparalytic facial hyperactivity (PPFHA) and 35 of whom had HFS. Control data was obtained from healthy sides 22 of 76 cases. "t test" and multiple comparisons were used for statistical evaluations. For o.oc muscle; when compared with the normal group, PPFHA group had significantly increased motor unit durations (p < 0.001), phase (p < 0.05), area (p < 0.05), turn (p < 0.05) and polyphasic potential numbers (p < 0.05) and HFS group had significantly increased amplitudes (p < 0.05), area (p < 0.05) and polyphasic potential numbers (p < 0.05). When patients groups were compared for the same muscle, PPFHA group had significantly increased MUP durations (p < 0.001) and number of turns (p < 0.05) as compared to HFS group. When o.or muscle values were compared with the normal group, PPFHA group had significantly increased durations (p < 0.001), phase (p < 0.05), area (p < 0.05) and turn numbers (p < 0.001) and polyphasic potential rates (p < 0.05) and area/amplitude values (p < 0.05), HFS group had significantly increased durations (p < 0.05), phase (p < 0.05), area (p < 0.05) and turn numbers (p < 0.05). When patient groups were compared for the same muscle, MUP duration was significantly increased (p < 0.05) in the PPFHA group as compared to HFS group. In conclusion, with the quantitative method, there is neurogenic involvement in the facial muscles of upper and lower halves in cases of HFS although lesser than PFP cases. This suggests that focal demyelination causes secondary axonal loss at least in some of the cases.