Dudley S. Dinner

Semiological seizure classification

Summary: We propose an epileptic seizure classification based exclusively on ictal semiology. In this semiological seizure classification (SSC), seizures are classified as follows:

Complications of invasive video-EEG monitoring with subdural grid electrodes

Objective: To evaluate the risk factors, type, and frequency of complications during video-EEG monitoring with subdural grid electrodes. Methods: The authors retrospectively reviewed the records of all patients who underwent invasive monitoring with subdural grid electrodes (n = 198 monitoring sessions on 187 patients; median age: 24 years; range: 1 to 50 years) at the Cleveland Clinic Foundation from 1980 to 1997. Results: From 1980 to 1997, the complication rate decreased (p = 0.003). In the last 5 years, 19/99 patients (19%) had complications, including two patients (2%) with permanent sequelae. In the last 3 years, the complication rate was 13.5% (n = 5/37) without permanent deficits. Overall, complications occurred during 52 monitoring sessions (26.3%): infection (n = 24; 12.1%), transient neurologic deficit (n = 22; 11.1%), epidural hematoma (n = 5; 2.5%), increased intracranial pressure (n = 5; 2.5%), and infarction (n = 3; 1.5%). One patient (0.5%) died during grid insertion. Complication occurrence was associated with greater number of grids/electrodes (p = 0.021/p = 0.052; especially >60 electrodes), longer duration of monitoring (p = 0.004; especially >10 days), older age of the patient (p = 0.005), left-sided grid insertion (p = 0.01), and burr holes in addition to the craniotomy (p = 0.022). No association with complications was found for number of seizures, IQ, anticonvulsants, or grid localization. Conclusions: Invasive monitoring with grid electrodes was associated with significant complications. Most of them were transient. Increased complication rates were related to left-sided grid insertion and longer monitoring with a greater number of electrodes (especially more than 60 electrodes). Improvements in grid technology, surgical technique, and postoperative care resulted in significant reductions in the complication rate.

Deep brain stimulation in epilepsy

Summary Since the pioneering studies of Cooper et al. to influence epilepsy by cerebellar stimulation, numerous attempts have been made to reduce seizure frequency by stimulation of deep brain structures. Evidence from experimental animal studies suggests the existence of a nigral control of the epilepsy system. It is hypothesized that the dorsal midbrain anticonvulsant zone in the superior colliculi is under inhibitory control of efferents from the substantia nigra pars reticulata. Inhibition of the subthalamic nucleus (STN) could release the inhibitory effect of the substantia nigra pars reticulata on the dorsal midbrain anticonvulsant zone and thus activate the latter, raising the seizure threshold. Modulation of the seizure threshold by stimulation of deep brain structures—in particular, of the STN—is a promising future treatment option for patients with pharmacologically intractable epilepsy. Experimental studies supporting the existence of the nigral control of epilepsy system and preliminary results of STN stimulation in animals and humans are reviewed, and alternative mechanisms of seizure suppression by STN stimulation are discussed.

Cortical somatosensory evoked potentials in response to hand stimulation

Somatosensory evoked potentials were recorded from chronically implanted subdural electrodes in six patients with intractable seizures. The following conclusions were reached: 1) The initial cortical negativity-positivity (N1 with a latency of about 20 msec and P2 with a latency of about 24 msec) recorded in the postcentral area was an expression of the classical primary surface positivity, but N1 was generated by the posterior pole of an early horizontal dipole in area 3b, and P2 was generated by the positive pole of a slightly delayed vertical dipole in area 1 and 2.2) P2 permitted the most accurate localization of the primary somatosensory area. 3) No potentials were elicited in the primary somatosensory area by stimulation of the ipsilateral hand. 4) No cortical potentials were seen at stimulation intensities below the sensory threshold. The cortical distribution of evoked potentials evoked by weak and strong intensities had significantly different distribution. 5) The recovery function of cortical evoked potentials showed a U-curve with an early period of facilitation (10 to 30 msec) followed by a prolonged period of subnormality which peaked at about 50 msec. The recovery curve at different cortical loci differed.

Dystonic posturing in complex partial seizures of temporal lobe onset: A new lateralizing sign

We observed unilateral dystonic posturing of an arm or leg in 41 complex partial seizures (CPS) from 18 patients. In all cases this was contralateral to the ictal discharge. Unilateral automatisms occurred in 39 of 41 seizures on the side opposite the dystonic limb. Version occurred in 11 of the 41 CPS to the same side as the dystonic posturing and always followed the posturing. Subdural recordings of seven seizures showed ictal onset from the mesial basal temporal lobe. At the onset of dystonic posturing, maximum ictal activity was in the basal temporal lobe with minimal involvement of the cerebral convexity. Unilateral dystonic posturing occurs frequently in CPS of temporal lobe onset and is a lateralizing sign with a high degree of specificity. It probably reflects spread of the ictal discharge to basal ganglia structures.

Supplementary motor seizures Clinical and electroencephalographic findings

The clinical and EEG features of 11 patients with seizures arising in the supplementary motor area (SMA) were reviewed. All patients underwent prolonged EEG with simultaneous video recording. Three patients had recordings and electrical stimulation of the SMA using subdural electrode arrays. All patients had preservation of consciousness during the seizure unless it became secondarily generalized. Tonic posturing of the extremities was present in all patients, and in seven it was present bilaterally. Adversive movements were not seen unless the seizure became secondarily generalized. Interictal and/or ictal abnormalities were present at or adjacent to the midline in ten patients. Seizures arising from the supplementary motor region are clinically distinct, and the diagnosis can almost always be verified with prolonged EEG/video recording.

Predictors of outcome after temporal lobectomy for the treatment of intractable epilepsy

To assess short- and long-term seizure freedom, the authors reviewed 371 patients who underwent anterior temporal lobectomy to treat pharmacoresistant epilepsy. The mean follow-up duration was 5.5 years (range 1 to 14.1 years). Fifty-three percent of patients were seizure free at 10 years. The authors identified multiple predictors of recurrence. Results of EEG performed 6 months postoperatively correlated with occurrence and severity of seizure recurrence, in addition to breakthrough seizures with discontinuation of antiepileptic drugs.

Video-electrographic and clinical features in patients with ictal asystole.

Objective: Ictal asystole (IA) is a rare event mostly seen in patients with temporal lobe epilepsy (TLE) and a potential contributor to sudden unexplained death in epilepsy (SUDEP). Clinical and video-electroencephalographic findings associated with IA have not been described, and may be helpful in screening for high risk patients. Methods: A database search was performed of 6,825 patients undergoing long-term video-EEG monitoring for episodes of IA. Results: IA was recorded in 0.27% of all patients with epilepsy, eight with temporal (TLE), two with extratemporal (XTLE), and none with generalized epilepsy. In 8 out of 16 recorded events, all occurring in patients with TLE, seizures were associated with a sudden atonia on average 42 seconds into the typical semiology of a complex partial seizure. The loss of tone followed after a period of asystole usually lasting longer than 8 seconds and was associated with typical EEG changes seen otherwise with cerebral hypoperfusion. Clinical predisposing factors for IA including cardiovascular risk factors or baseline ECG abnormalities were not identified. Conclusion: Ictal asystole is a rare feature of patients with focal epilepsy. Delayed loss of tone is distinctly uncommon in patients with temporal lobe seizures, but may inevitably occur in patients with ictal asystole after a critical duration of cardiac arrest and cerebral hypoperfusion. Further cardiac monitoring in patients with temporal lobe epilepsy and a history of unexpected collapse and falls late in the course of a typical seizure may be warranted and can potentially help to prevent sudden unexplained death in epilepsy.

Association between the Epworth Sleepiness Scale and the Multiple Sleep Latency Test in a Clinical Population

No statistically or clinically significant association was seen between scores on the subjective Epworth Sleepiness Scale and results of the objective mean sleep latency test. These tests may evalu...

The lateralizing significance of versive head and eye movements during epileptic seizures.

We studied 37 patients who had head and eye turning during 74 spontaneous epileptic seizures. Videotapes and EEGs were analyzed independently. Turning movements were classified without knowledge of EEG or clinical data as either versive (unquestionably forced and involuntary, resulting in sustained unnatural positioning) or nonversive (mild, unsustained, wandering, or seemingly voluntary). Videotape observations were then correlated with the EEG location of seizure onset. Contralateral versive head and eye movements occurred during 61 seizures in 27 patients, but ipsilateral versive movements did not occur. Nonversive lateral head and eye movements occurred ipsilaterally and contralaterally with equal frequency and were nonlocalizing, but versive movement was a reliable lateralizing sign.