Effects of monotherapy and polytherapy on the blink reflex in epileptic patients

Blink reflex in progressive myoclonic epilepsies

PURPOSE

Progressive myoclonic epilepsies (PME) include a heterogeneous group of disorders. The brainstem is involved in these disorders, as demonstrated by neuroimaging and autopsy studies. The blink reflex (BR) is characteristically elicited after supraorbital electrical stimulation. The BR has two components, an ipsilateral R1 and bilateral R2 (R2 and R2c). The central generator of the BR is the brainstem. In this study, we aimed to investigate the functional status of the brainstem using the BR in PME cases with different etiological factors.

METHODS

We prospectively included 17 patients with a diagnosis of PME (8 male, 47.1%) who were examined between June 2009 and June 2012. For comparison, we included 41 healthy volunteers (18 male 43.9%) who did not have any neurological or systemic diseases. We recorded responses bilaterally over the orbicularis oculi muscles after supraorbital stimulation in all participants.

RESULTS

The R1 and R2 components of the BR were obtained in all healthy subjects with normal latencies, whereas abnormalities in the R2 and R2c components were observed at significantly higher rates in the PME patients. The mean latencies of the bilateral R2 and R2c components were significantly prolonged, and the amplitudes were diminished in the PME patients. Disease duration and the use of multiple antiepileptic drugs were related to abnormal R2s.

CONCLUSION

The abnormalities of the R2 and R2c components of the BR confirmed the inhibition of the reticular formation. The findings are probably related to disease processes and partially due to the use of multiple antiepileptic drugs.

Eye-blink behaviors in 71 species of primates

The present study was performed to investigate the associations between eye-blink behaviors and various other factors in primates. We video-recorded 141 individuals across 71 primate species and analyzed the blink rate, blink duration, and “isolated” blink ratio (i.e., blinks without eye or head movement) in relation to activity rhythms, habitat types, group size, and body size factors. The results showed close relationships between three types of eye-blink measures and body size factors. All of these measures increased as a function of body weight. In addition, diurnal primates showed more blinks than nocturnal species even after controlling for body size factors. The most important findings were the relationships between eye-blink behaviors and social factors, e.g., group size. Among diurnal primates, only the blink rate was significantly correlated even after controlling for body size factors. The blink rate increased as the group size increased. Enlargement of the neocortex is strongly correlated with group size in primate species and considered strong evidence for the social brain hypothesis. Our results suggest that spontaneous eye-blinks have acquired a role in social communication, similar to grooming, to adapt to complex social living during primate evolution.

Brainstem dysfunction in alternating hemiplegia of childhood: a neurophysiological study

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.

Blink reflex in end-stage-renal disease patients undergoing hemodialysis

This study analyses the blink reflex in 20 adult male patients with terminal chronic renal failure undergoing hemodialysis. Abnormalities were found in ten patients (50%), eight of them with conduction studies showing axonal peripheral neuropathy. Dialysis time was longer for patients with blink reflex alterations (median 55.1 months) than for patients with normal blink reflex (median 36.3 months). Different types of early R1 and late R2 component abnormalities were recorded. The late response abnormalities may indicate subclinical functional or anatomical impairment of the low brainstem reticular formation in patients with chronic renal failure.

Early seizures after acute stroke: a study of 1,640 cases

We evaluated prospectively the occurrence of seizures within 15 days of a first stroke or transient ischemic episode in 1,640 patients to study relation between seizures and type of stroke. Seizures occurred in 90 patients (5.4%), including 36 (4.4%) of 814 with infarct owing to atheroma, 21 (16.6%) of 126 with infarct owing to cardiogenic embolus, 3 (1%) of 273 owing to lacunar infarct, 5 (1.9%) of 259 owing to transient ischemic attack (TIA), 21 (16.2%) of 129 owing to supratentorial hematoma, and 4 (16.6%) of 24 owing to subarachnoid hemorrhage. Thirteen (14.6%) of 89 subcortical infarcts were associated with seizures. Seizures were the initial sign of stroke in 80 (89%) of 90 cases and were usually single and partial. Seizure symptoms were most often motor, sensory, or visual.