R1 Latency Research Articles

Acoustic startle response in patients with orthostatic tremor

Background and aimOrthostatic tremor is a high frequency tremor predominantly on calf muscles during standing. Brainstem is the most probable generator in the pathogenesis since it comprises bilaterally projecting centers regulating stance or tone. We aimed to investigate the functional role of brainstem through the evaluation of acoustic startle response in primary orthostatic tremor patients. Patients and methodWe included 7 (2 males) consecutive patients and 13 (5 males) healthy volunteers. Diagnosis was confirmed by polymyographic surface electromyography. All subjects underwent acoustic startle response and blink reflex investigations. ResultsPresence rate (71.4% vs. 100%, p=0.042) and response rate (27.5% vs. 40.5%, p=0.047) of total acoustic startle response were lower in patient group. Similarly, probability over orbicularis oculi was lower among patients (p=0.003). However, blink reflex was observed in all patients and healthy volunteers and latencies of startle and blink reflexes were similar between groups. ConclusionsIn our patient group, normal response rate and latencies of R1 and R2 show structural integrity of at least blink reflex circuit at brainstem. On the other hand, suppressed response rates probably reflect decreased excitability of auditory startle reflex pathway.

Blink reflex prepulse inhibition and excitability recovery: Influence of age and sex

ObjectiveAge and sex affect various reflexes in healthy humans. Their respective influence on prepulse inhibition (PPI) of the trigeminofacial blink reflex (BR) and BR excitability recovery has not as yet been investigated in detail. MethodsWe studied the trigeminofacial BR bilaterally in 62 healthy volunteers (31 males, age 41.0±13.2years, mean±SD, 31 females, 39.2±11.7years) following right supraorbital nerve stimulation. Single sweeps were recorded either alone (n=8) or conditioned by a prepulse applied 100ms earlier to the dominant index finger though ring electrodes (n=8). Latency and amplitude of the ipsilateral R1 component, as well as latency and area-under-the-curve of the ipsilateral R2 and contralateral R2c components were measured in single traces and then averaged per subject. BR excitability recovery was established bilaterally following right supraorbital nerve stimulation with paired pulses. Six responses were averaged on-line per interstimulus interval (ISI 160, 300, and 500ms). ResultsUnconditioned BR did not differ significantly between males and females, but R2 and R2c latencies increased with age. Prepulse stimulation caused significant facilitation of R1 (latency and amplitude), and inhibition of R2 and R2c (latency and area), irrespective of age. PPI of R2 and R2c area was significantly more pronounced in men. BR excitability recovery was significantly influenced by age, but not by sex. Multiple regression showed inverse correlation of age with conditioned R2 and R2c area at ISI 300ms and 500ms (P<0.01 each), indicating reduced excitability recovery. No parameter showed significant interaction of age×sex. ConclusionThese data indicate less pronounced PPI of the trigeminofacial BR in females, concurring with previous reports of sex differences in protective reflexes, but also suggesting less rigorous filtering of information flow to the brain in females. Reduced BR excitability to paired-pulse stimulation may counteract age-related disinhibition of brainstem interneuronal circuitry. SignificanceThe present findings allow new insight into human brainstem physiology.

Narcolepsy–cataplexy: deficient prepulse inhibition of blink reflex suggests pedunculopontine involvement

Hypocretin (orexin) deficiency plays a major role in the pathophysiology of narcolepsy-cataplexy. In animal models, hypocretinergic projections to the pedunculopontine nucleus are directly involved in muscle tone regulation mediating muscle atonia - a hallmark of cataplexy. We hypothesized that pedunculopontine nucleus function, tested with prepulse inhibition of the blink reflex, is altered in human narcolepsy-cataplexy. Twenty patients with narcolepsy-cataplexy and 20 healthy controls underwent a neurophysiological study of pedunculopontine nucleus function. Blink reflex, prepulse inhibition of the blink reflex and blink reflex excitability recovery were measured. Blink reflex characteristics (R1 latency and amplitude, and R2 and R2c latency and area under the curve) did not differ between patients and controls (P > 0.05). Prepulse stimulation significantly increased R2 and R2c latencies and reduced R2 and R2c areas in patients and controls. However, the R2 and R2c area suppression was significantly less in patients than in controls (to 69.8 ± 14.4 and 74.9 ± 12.6%, respectively, versus 34.5 ± 28.6 and 43.3 ± 29.5%, respectively; each P < 0.001). Blink reflex excitability recovery, as measured by paired-pulse stimulation, which is not mediated via the pedunculopontine nucleus, did not differ between patients and controls (P > 0.05). Our data showed that prepulse inhibition is reduced in narcolepsy-cataplexy, whereas unconditioned blink reflex and its excitability recovery are normal. Because the pedunculopontine nucleus is important for prepulse inhibition, these results suggest its functional involvement in narcolepsy-cataplexy.

Hemifacial spasm associated with intraparenchymal brain stem tumor

parenchymal brain stem lesions remains unclear. A 58-year-old woman, who had been experiencing slowly progressive left facial weakness, diplopia, and dysphagia for 7 years, developed intermittent facial twitches around her left orbicularis oculi, lower face, and platysma. On examination, she had severe left facial weakness, left abducens palsy, moderate dysarthria, tongue atrophy, and mild right hemiparesis. Intermittent contractions were visible in left frontalis, orbicularis oculi, and zygomaticus muscles. These occurred as single twitches and as brief series of contractions (Video). Magnetic resonance imaging revealed a nonenhancing lesion (maximum diameter, 22 mm) in the left lower pons and the central and left upper medulla, with increased signal on T2-weighted and proton density images, consistent with a lowgrade pontomedullary glioma or hamartoma. Notably, the lesion involved the facial nucleus and spared the root exit zones of both facial nerves (Fig. 1). Nerve conduction studies showed significantly reduced amplitudes in the left facial nerve, especially in the orbicularis oris and mentalis branches; however, responses were evident in all facial muscles tested. In blink reflex studies, left supraorbital nerve (SON) stimulation produced normal-latency ipsilateral R1 and significantly prolonged ipsilateral and normal contralateral R2 latencies (55.3 and 39.9 ms, respectively). Right SON stimulation produced normal ipsilateral R1 and R2 latencies, but absent contralateral R2 response. These findings suggest interruption of normal inputs to the left facial nucleus. They are also evidence of cross-communication that could originate from the intramedullary portion of the facial nerve or from the facial nucleus. Electromyography revealed evidence of chronic but not acute neurogenic changes in affected facial muscles. Discharges consistent with HFS were recorded from the left orbicularis oris during an episode of repeated spasm-like contractions, typical of HFS, of the left cheek and perioral muscles. The left orbicularis oris had 1þ fasciculations, as well as intermittent single discharges associated with clonic spasms, typical of HFS. No myokymic discharges were observed. Although involuntary facial muscle contractions have been reported in association with intraparenchymal lesions, 4,5 these conditions may have represented ‘‘spastic paretic hemifacial contracture’’ (SPHC), which is characterized by sustained facial muscle contractions and continuous muscle activity. 6,7 In 1 case 4 electromyography showed high-frequency bursts, but clonic spasms were not mentioned. In the other case 5 contractions were sustained, and electrophysiology showed tonic, nearly continuous activity of the facial nerve and high-frequency discharges in its innervated muscles. Both cases may thus have represented SPHC rather than HFS. To our knowledge, therefore, the present report is the first description of facial twitching with the clinical and electrophysiologic hallmarks of idiopathic HFS, associated with an intraparenchymal brain lesion affecting the facial nucleus but not the facial nerve’s root. Legend to Video. Hemifacial spasm and signs of brain stem dysfunction in the patient described in the present report. The video shows intermittent involuntary muscle contractions mainly involving the zygomaticus and to a lesser degree the frontalis and orbicularis oculi on the left side of the face. These occur at variable intervals, at times as single twitches and other times as brief trains of contractions.

The effect of paired stimuli on blink reflex latencies in normal subjects

In this study we assessed the effect of paired stimuli on the latencies and amplitudes of the blink reflex. Blink reflexes were performed with single and paired (5-ms interstimulus interval) stimuli in 47 patients. The changes in latencies between paired and single stimuli were calculated. Paired stimulation produced two types of R1 waveform morphologies: single- and double-peaked waveforms. Increases in R1 and contralateral R2 latencies with paired stimulation were significantly higher in those with single-peaked R1 responses compared to those with double-peaked R1 responses. Interpreting the blink reflex latencies using paired stimulation requires visualization of the R1 waveform morphology. A double-peaked R1 response requires no change in normal latency values, but the latency of a single-peaked R1 should be interpreted from the second shock artifact. The effect on the R2 latency is variable.

The value of BR in evaluating the occurrence of DFP after MVD for HFS and the mechanism of DFP

Objective To observe the change in blink reflex( BR) before and after microvascular decompression (MVD) for hemifacial spasm (HFS) and discuss the possible mechanism of delayed facial palsy( DFP). Method 60 patients with HFS were examined before and every two days after the surgery and the occurrences of DFP were observed. Results In 56 cases DFP did not appear, but BR examination still revealed the postoperative short - term prolongations in the latencies of Rl and R2. The latencies of R1 returned to preoperative levels in 5 days and the latencies of R2 returned to preoperative levels in 3 days after the operations. DFP occurred in 4 cases during 6-15 days after MVD, in which the prolongations in the latencies of Rl were gradual and irreversible. Conclusions The functions of Ⅶ were slightly injuryed during MVD. And most of cases(93%) could recover in 5 days, while the dysfunction of Ⅶ were getting worse in the others in which BR tests showed gradual prolongations in the latencies of R1 or the disappearance of R1 waveform. DFP was finally occurred to these patients. The changes in Rl - wave have some important value in evaluating the possibility of the occurrence of DFP after MVD for HFS. Key words: Hemifacial spasm; Microvascular decompression; Blink reflex; Delayed facial palsyx

Blink and masseter inhibitory reflexes in Parkinson's disease

Idiopathic Parkinson's disease (PD) is a chronic, progressive, neurodegenerative disorder with prevalence from 60 to 187 per 100 000 persons in general population. The aim of the study was to determine the abnormalities of the blink reflex (BR) and the masseter inhibitory reflex (MIR) in parkinsonian patients, as indices of the functional status of brainstem neuronal network, and abnormality level dependence on disease progression. The investigation was conducted at the Clinic of Neurology, Clinical Center Nis, comprising a group of 60 subjects of both sexes, suffering from idiopathic Parkinson's disease in I-IV stages, according to the Hoehn and Yahr scale. The control group included 30 healthy subjects of both sexes and corresponding age. Testing of the patients was performed during the "on" phase by registering MIR and BR. Latency of polysynaptic R2 and R2' blink reflex responses and latency of polysynaptic S2 response, as well as a silent period of MIR, are linearly shortened in the subjects with PD, and more expressed in the subsequent stages of the disease compared to the control group. There is a positive correlation between the applied neurophysiological tests results and clinical stage of PD.

Nitroglycerin sensitises in healthy subjects CNS structures involved in migraine pathophysiology: Evidence from a study of nociceptive blink reflexes and visual evoked potentials

Nitroglycerin (NTG), a NO donor, induces an attack in migraine patients approximately 4–6h after administration. The causative mechanisms are not known, but the long delay leaves room for a central effect, such as a change in neuronal excitability and synaptic transmission of various CNS areas involved in pain and behaviour including trigeminal nucleus caudalis and monoaminergic brain stem nuclei. To explore the central action of NTG, we have studied its effects on amplitude and habituation of the nociceptive blink reflex (nBR) and the visual evoked potential (VEP) before, 1h and 4h after administration of NTG (1.2mg sublingual) or placebo (vehicle sublingual) in two groups of 10 healthy volunteers. We found a significant decrease in nBR pain and reflex thresholds both 1 and 4h post-NTG. At the 4h time point R2 latency was shorter (p=0.04) and R2 response area increased (p<0.01) after NTG but not after placebo. Habituation tended to become more pronounced after both NTG and placebo administration. There was a significant amplitude increase in the 5th VEP block (p=0.03) at 1h after NTG and in the 1st block (p=0.04) at 4h. VEP habituation was replaced by potentiation at both delays after NTG; the change in habituation slope was significant at 1h (p=0.02). There were no significant VEP changes in subjects who received sublingual placebo. In conclusion, we found that in healthy subjects sublingual NTG, but not its vehicle, induces changes in a trigeminal nociceptive reflex and an evoked cortical response which are comparable to those found immediately before and during an attack of migraine. These changes could be relevant for the attack-triggering effect of NTG in migraineurs.

Delayed Blink Reflex in Dementia With Lewy Bodies Is Sensitive to Cholinergic Modulation

To assess the possible responsiveness of blink reflex alterations present in dementia with Lewy bodies (DLB) to treatment with cholinesterase inhibitors. Twenty-six patients with DLB and 20 patients with Alzheimer disease underwent clinical, neuropsychological (including assessment of cognitive fluctuations, with the Cognitive Assessment of Fluctuations and the One-Day Fluctuation Assessment questionnaires), and the blink reflex evaluation at baseline, 1 week after vitamin E administration (to assess test-retest reliability), and 1 and 2 weeks after donepezil administration at the dose of 10 mg/d. Results were compared with data obtained from 30 healthy controls treated with vitamin E capsules for 2 weeks. Treatment with donepezil did not cause modifications of cognitive or motor performances in both groups of patients. In DLB patients, One-Day Fluctuation Assessment scores were modified by donepezil treatment with a mean reduction of 2.8 +/- 1.8 compared with baseline (P < 0.05). After 2 weeks of treatment with donepezil, R2 latency was significantly decreased in DLB patients. The mean R2 latency reduction was by 3.0 +/- 3.2 milliseconds (P < 0.0001 compared with baseline). R2 mean latency reduction was significantly correlated with R2 mean latency delay at baseline (Spearman rho = 0.8). Short-term donepezil administration can correct the alterations of the blink response together with the daily occurrence of cognitive fluctuations present in DLB patients.

Blink Reflex Alterations in Diabetic Patients with or without Polyneuropathy

The main aim of this study is to evaluate the role of blink reflex for early diagnosis of cranial neuropathy in diabetic patients with or without polneuropathy. Ninety-five diabetic patients were included in the present study for the evaluation of blink reflex. The diabetic patients were divided into two groups according to having diabetic neuropathy or not. Both R1, R2i and R2c latencies in all diabetic patients with or without polyneuropathy were prolonged relative to controls and the differences were statistically significant (p < .001). R1 latencies in diabetic patients with polyneuropathy were prolonged relative to diabetic patients without polyneuropathy and the differences were statistically significant (p < .001). These findings presumably reflect that facial nerve is severly involved in diabetic polyneuropathy. Finally blink reflex is of value in detection of clinically silent intraaxial brainstem functional abnormalities or extraaxial lesions in diabetic patients before peripheral neuropathy.

Occipital Nerve Blockade in Chronic Cluster Headache Patients and Functional Connectivity Between Trigeminal and Occipital Nerves

Headache syndromes often involve occipital and neck symptoms, suggesting a functional connectivity between nociceptive trigeminal and cervical afferents. Although reports regarding effective occipital nerve blockades in cluster headache exist, the reason for the improvement of the clinical symptoms is not known. Using occipital nerve blockade and nociceptive blink reflexes, we were able to demonstrate functional connectivity between trigeminal and occipital nerves in healthy volunteers. The R2 components of the nociceptive blink reflex and the clinical outcome in 15 chronic cluster headache patients were examined before and after unilateral nerve blockade of the greater occipital nerve with 5 ml prilocain (1%) on the headache side. In contrast to recent placebo-controlled studies, only nine of the 15 cluster patients reported some minor improvement in their headache. Six patients did not report any clinical change. Exclusively on the injection side, the R2 response areas decreased and R2 latencies increased significantly after the nerve blockade. These neurophysiological and clinical data provide further evidence for functional connectivity between cervical and trigeminal nerves in humans. The trigeminocervical complex does not seem to be primarily facilitated in cluster headache, suggesting a more centrally located pathology of the disease. However, the significant changes of trigeminal function as a consequence of inhibition of the greater occipital nerve were not mirrored by a significant clinical effect, suggesting that the clinical improvement of occipital nerve blockades is not due to a direct inhibitory effect on trigeminal transmission.

Blink Reflex in Hypothyroidism

Aim: The aim of the present study was to evaluate the usefulness of the blink reflex as a method for obtaining an early diagnosis of central nervous system dysfunction in hypothyroid patients who do not have signs or symptoms of nervous system dysfunction. Materials and Methods: Forty-two patients (3 males, 39 females), mean age 40 (±11), with newly diagnosed primary hypothyroidism and 30 healthy control subjects were included in the study. In all patients, the cause of hypothyroidism was chronic autoimmune thyroiditis. For blink reflex testing, subjects lay supine on a bed in a warm room with eyes gently closed. Recordings were performed with an EMG machine (Nihon Kohden/Neuropack), with a filter setting of 20 Hz to 10 kHz, using an analysis time of 50 ms. Recordings were performed with surface recording electrodes (Dantec 13K60, Copenhagen, Denmark). Results: Second ipsilateral response (R2Y) and second contralateral response (R2C) latencies in hypothyroidism were prolonged relative to controls, and the differences were statistically significant (P < 0.001 and P < 0.001, respectively). Latency of R1, R2Y, and R2C did not correlate with free T3, free T4, or TSH values in the hypothyroid group. Conclusion: The finding of abnormal blink reflex responses in hypothyroid individuals raises the notion that they may be useful in detecting early changes and in the follow-up of the patients with the disorder.

Electrophysiological findings of acute peripheral facial palsy in diabetic and non-diabetic patients

The aim of this study is to investigate the role of diabetes mellitus on the clinical and electrophysiological findings of peripheral facial palsy (PFP), the effect of the diabetes duration and polyneuropathy on the electrophysiological parameters. A total of 32 diabetic and 40 non-diabetic patients with peripheral facial palsy were included. All patients were divided into two subgroups based on the time of electrophysiological examinations: within the first 15 days versus within 16–30 days. Neuropathy symptoms and the results of neurological examinations and electrophysiological findings were recorded. The findings of electroneurography (EnoG), blink reflex (BR) evaluation, and needle electromyography (EMG) indicated statistically significant blink reflex abnormalities in diabetic patients compared to non-diabetics. Delay in the latency was more remarkable in the R2 component than in the R1 ( p < 0.001). The delay in the R1 latency was also observed in the non-affected side for diabetic patients. The longer duration of the diabetes caused significant delay on the blink reflex latency on both the affected and non-affected sides for R1 component ( p = 0.019, p = 0.041, respectively). In contrary, neither the diabetes duration nor the age of the patients correlated with the clinical severity of facial palsy, fiber loss, fibular nerve compound muscle action potential amplitudes, and the nerve conduction velocities.

+ − Reconstruction of the intratemporal facial nerve using interposition nerve graft: time course of recovery in facial movement and electrophysiological findings

Conclusions. Data about the recovery course of facial function after intratemporal facial nerve reconstruction using interposition nerve graft would provide useful information for clinicians to understand the regenerative process of the facial nerve after this type of surgery. It would also enable them to obtain informed consent from the patients by preoperatively explaining the predicted outcome of the postoperative facial paralysis. Objective. The purpose of this study was to describe the recovery course of facial movement and electrophysiological findings after intratemporal facial nerve reconstruction using interposition graft. Patients and methods. Five patients who underwent reconstruction of the facial nerve using interposition nerve graft immediately after facial nerve excision during surgery for temporal bone lesions were included in this study. Each patient was evaluated for facial movement (Yanagihara score), blink reflex (BR), and electroneurography (ENoG) preoperatively and postoperatively. Results. Improvement in facial movement began 8–10 months postoperatively. The score then gradually increased, and reached a plateau level by 2 years following surgery. The final score in four of the five patients ranged from 20 to 24 points, while the facial score of one patient only reached 12 points even at 3 years after surgery. All patients demonstrated moderate to severe synkinesis. The reappearance of R1 in BR occurred 7–10 months postoperatively, almost simultaneously with the beginning of recovery of facial movement. The latency of R1 on the operated side became shortened with increasing postoperative time, although it remained considerably longer than that on the unoperated side, even after 2 postoperative years. The onset of recovery of ENoG value (10–12 months postoperatively) was always delayed compared with the actual facial movement recovery and never returned to the level in the unoperated side.

The blink reflex in “chronic migraine”

ObjectivesActivation of the trigeminovascular system and sensitisation of brainstem trigeminal nuclei are thought to play an important role in migraine. The aim of this study was to investigate the blink reflex and its habituation in patients with “chronic migraine”. MethodsWe studied 35 patients suffering from “chronic migraine” (IHS classification criteria) outside and during a spontaneous attack, and 35 control subjects. An EMG device with a specific habituation test program was used to elicit and record blink reflex responses and to randomly repeat stimulations at different time intervals so as to induce habituation. ResultsThe R1 and R2 latencies, amplitudes and areas of the basal blink reflex were similar in patients studied both outside and during an attack as well as in control subjects, whereas the blink reflex habituation responses were markedly reduced in patients studied outside an attack. The percent changes in the R2 areas from the baseline values, obtained when stimuli were delivered at time intervals of 10, 5, 4, 3, 2 and 1s, were statistically different (p<0.01–p<0.001) from those of the same patients studied during a migraine attack and of those of control subjects. There was a significant correlation between decreased habituation of the blink reflex and a higher frequency of attacks. The stimulus intensities of the blink reflex (multiples of the detection threshold intensities) were significantly lower (p<0.001) on the side affected, or more severely affected, by headache in patients studied during a migraine attack. ConclusionsThe decreased habituation of the blink reflex outside an attack reflects abnormal excitability in “chronic migraine”, which normalizes during the attacks. The inverse correlation between the frequency of attacks and habituation responses confirms the abnormal excitability induced by the high frequency of attacks. Central sensitisation mechanisms (allodynia) may explain the lower detection thresholds observed on the side affected by headache in patients during the attacks. SignificanceThe blink reflex and its habituation may help shed light on the subtle neurophysiological changes that occur in migraine patients between and during attacks.

Role of Blink Reflex in Diagnosis of Subclinical Cranial Neuropathy in Diabetic Mellitus Type II

Peripheral neuropathy (PN) is one of the late complications of diabetes mellitus. Cranial nerves III, VII, and V are among the most commonly affected in diabetic patients. Traditional electrodiagnosis (Edx) studies are a useful method for diagnosis of PN and symptomatic cranial neuropathy, and may not be useful for detecting subclinical involvement of cranial nerves. The main objective of this study is to evaluate the role of blink reflex (BR) for early diagnosis of cranial neuropathy in diabetic patients with PN. A prospective study was performed on NIDDM patients with PN. One hundred eighty-eight subjects were included in our study in which 142 acted as healthy subjects and 46 as diabetic patients. Patients were excluded with prior history of cranial nerve lesions, stroke, or any other disease with polyneuropathy or drug-induced neuropathy. Routine nerve conduction studies were performed, and only patients with PN were included in this study. Abnormalities were found in 54.4% of patients. R1, IR2, and CR2 were prolonged relative to the healthy group. Statistically there was no significant difference in R/D ratio of patients (P=0.201). Also, there was a positive correlation between R1, IR2, and CR2 latencies with duration of diabetes and severity of polyneuropathy, but not for R/D. The greatest correlation was shown in R1 latency (69.9% abnormality). BR is a noninvasive and very useful method for the evaluation and diagnosis of subclinical cranial nerve involvement in diabetic patients.

Brainstem Dysfunction in Alternating Hemiplegia of Childhood

Six patients with alternating hemiplegia of childhood (AHC) underwent motor evoked potentials (MEPs), somatosensory evoked potentials (SEPs) and blink reflex recording. No SEP abnormality was found. As for MEP recording, central conduction time did not differ between patients studied during either interictal or ictal phase, and normal subjects, suggesting that the pyramidal system function is spared. In blink reflex recording, the latencies of both the ipsilateral (iR2) and contralateral (cR2) R2 components were significantly longer (P<0.01) in patients during the interictal phase than in normal subjects. Moreover, the iR2 and cR2 areas were significantly reduced (P<0.01) in patients during the interictal phase, compared with normal subjects. During the ictal phase, the ipsilateral R2 latency was significantly decreased after stimulation of the hemiplegic side, compared with the interictal phase (P<0.05). The blink reflex abnormalities suggest a brainstem dysfunction, which may be linked to the pathophysiological mechanisms of the disease.

Functional Connectivity between Trigeminal and Occipital Nerves Revealed by Occipital Nerve Blockade and Nociceptive Blink Reflexes

Headache syndromes often suggest occipital and neck involvement, although it is still unknown to what extent branches of segment C1-C3 contribute actively to primary headache. Pain within the occipital area may be referred to the trigeminal territory. However, a modulation of trigeminal transmission by affecting cervical input in humans has not been elucidated so far. A convergence of cervical and trigeminal input at the level of the caudal part of the trigeminal nucleus in the brainstem has been suggested due to anatomical and neurophysiological studies in animals. We examined the R2 components of the nociceptive blink reflex responses in 15 healthy subjects before and after unilateral nerve blockade of the greater occipital nerve with 5 ml prilocain (1%). R2 response areas (AUC) decreased and the R2 latencies increased significantly after the nerve blockade only on the side of injection. AUC and latencies on the non-injection side remained stable. Thresholds for sensory or pain perception did not differ significantly between the repeated measurements on both sides. Our findings extend previous results related to anatomical and functional convergence of trigeminal and cervical afferent pathways in animals and suggest that the modulation of this pathway is of potential benefit in primary headache disorders.

Differences of blink-reflex abnormalities in patients suffering from idiopathic and symptomatic trigeminal neuralgia

We investigated the brainstem blink reflex in patients suffering from idiopathic and symptomatic trigeminal neuralgia to establish possible dysfunction in the reflex cycle and determine eventual differences between the two disease types. The study included 35 patients with idiopathic disease and seven patients with symptomatic disease, their results compared with those of 50 normal controls. We stimulated the forehead afferents of the supraorbital nerve and recorded the response from both orbicularis oculi muscles. We tested latencies of bilateral late components (R2, R2'), irritative R3 component and the incidence of R3 component. The patients with idiopathic trigeminal neuralgia showed normal parameters of blink reflex, except for the greater incidence of R3 component. Patients with symptomatic trigeminal neuralgia showed prolonged latencies of R2, R2' and R3 components when stimulating the afflicted side, but no significant difference in incidence of R3 component compared with the control group. The results indicate that abnormalities of blink reflex are significantly different in the two groups of patients. The high incidence of R3 component seems to be typical of idiopathic disease, whereas the prolonged latencies of late reflex components after stimulation of the afflicted side seem to be typical for symptomatic disease. These results suggest that testing the blink reflex may prove a significant aid in distinguishing the idiopathic and symptomatic disease types.

Blink Reflex Abnormalities in Chronic Alcoholics

Purpose: The aim of the present study was to evaluate the efficacy of blink reflex as a method for obtaining early diagnosis of cranial nerve involvement in alcoholic patients. Materials and Methods: The study was conducted on 30 male alcoholics with a mean age of 43 years. They had histories of alcohol abuse for at least 6 years (mean: 25). At the time of recording, they had undergone detoxification treatment for a mean of 27 days. Results: R1 (early response), R2Y (second ipsilateral response), and R2C (second contralateral response) latencies in alcoholics were prolonged relative to controls and the differences were statistically significant (p < 0.02, p < 0.001, p < 0.001, respectively). According to the defined criteria, 40% of the patients had abnormal responses, and the most common abnormality was the unilateral prolongation of R1 (13%). Conclusion: Finding abnormal blink reflex responses in alcoholic patients has suggested that blink reflex testing is a useful method for the evaluation of subclinical cranial nerve involvement in alcoholic patients. Blink reflex testing may be useful in detecting early changes and in the follow-up of alcoholic disorder.