EEG and seizures in children with hemolytic-uremic syndrome

The EEG results of 11 children, ages 1-15 years, who presented with hemolytic-uremic syndrome complicated by seizures 3-10 days after the prodrome were studied. In four children who experienced generalized tonic-clonic seizures, the EEGs demonstrated diffuse delta slowing with no focality. All recovered without neurological deficit or a residual seizure disorder. Of seven children who experienced partial seizures, six had structural lesions on cranial computed tomography and residual focal neurological deficits with epilepsy. The EEGs in two patients revealed focal spikes and slowing consistent with the lateralization of the partial seizures, in four it was characterized by atypical "burst suppression," and in one showed epochs of high-amplitude delta slowing alternating with generalized suppression. Although episodic and generalized burst suppression is usually regarded as a grave prognostic indicator, all four subjects recovered.

Lack of pathologic changes in human temporal lobes after transcranial magnetic stimulation

Most animal studies have failed to demonstrate pathologic changes in the brain after transcranial magnetic stimulation (TMS). Nevertheless, vacuolar lesions in the cortex of rats after TMS have been reported. We report the first histopathologic studies of human brains after TMS in 2 patients with epilepsy who underwent temporal lobectomies. They had been involved in a study to determine the speech-dominant hemisphere by TMS and had received approximately 2,000 stimuli centered over the resected temporal lobe. Histologic study of the surgical specimens did not show any lesions attributable to TMS in these 2 patients.

The heating of metal electrodes during rapid-rate magnetic stimulation: a possible safety hazard

The temperature of electrodes and metal disks positioned close to a coil was measured during rapid-rate magnetic stimulation. The temperature rise ranged from a fraction of a degree to almost half a degree per stimulus pulse and increased with the electrical conductivity of the metal, the square of the electrode radius and the square of the stimulus strength, and was independent of the electrode thickness. During a brief high-frequency train, the temperature increase from each pulse added; during a long, high-frequency train the temperature increase approached a steady state. After the stimulus ended, an electrode on the arm cooled with a time constant of about 45 sec. A standard silver EEG electrode on the surface of the skin did not increase in temperature enough to induce a skin burn if the stimulating rate was below 0.4 Hz or the total number of stimuli was less than 20. Heating was reduced by cutting gaps in the electrode.

No evidence of hearing loss in humans due to transcranial magnetic stimulation

Prompted by the description of hearing loss in rabbits exposed to the acoustic artifact of magnetic stimulation, we compared the results of audiologic studies before and after exposure to transcranial magnetic stimulation in humans. We found no evidence of temporary or permanent threshold shifts in any of the subjects, even in those exposed to transcranial magnetic stimulation repeatedly for several years. Risk of hearing loss from the acoustic artifact of magnetic stimulation, as evaluated by audiograms, tympanograms, acoustic reflexes, and auditory evoked potentials, seems to be small in humans.

Simple reaction time to focal transcranial magnetic stimulation. Comparison with reaction time to acoustic, visual and somatosensory stimuli

We studied the effect of different go-signals on the reaction time in nine normal human subjects trained to respond by rapidly flexing one arm. Reaction times to auditory stimuli were shorter than those to visual or somatosensory stimuli, and were inversely correlated with the stimulus intensity. The reaction time was longest to a transcranial (magnetic or electric) stimulus delivered over the contralateral motor cortex that was sufficiently strong to induce a motor evoked potential in the responding biceps. Conversely, reaction time was shortest to either subthreshold transcranial stimulation over the same scalp position or to transcranial stimulation over the ipsilateral motor cortex regardless of intensity. Suprathreshold transcranial stimulation to the motor cortex seems to transiently inhibit the neurons responsible for initiation of motor programs involving muscles in which motor evoked potentials have been induced, thereby prolonging the reaction time. On the other hand, a subthreshold stimulus either disinhibits or directly activates such neurons leading to a shorter reaction time. Transcallosal connections between the motor cortices may account for the short reaction time to ipsilateral transcranial stimulation.

Chronic, habitual cocaine abuse and kindling-induced epilepsy: a case report

Kindling has been suggested as a possible mechanism for cocaine-induced seizures in chronic cocaine abusers, even though no convincing examples have been reported. We report a 37-year-old woman who initially experienced generalized tonic-clonic seizures (GTC) only immediately after "crack" use. She had a normal examination, negative family or past history for seizures, and normal cranial computed tomography and EEG. After she had abused cocaine almost daily for 2 years, her EEG demonstrated bitemporal slowing with independent spikes, and seizures were no longer temporally associated with acute cocaine use. Thereafter, despite complete abstinence from cocaine and treatment with phenytoin, she continued to experience four to six GTC a month. In light of the lack of other predisposing factors for epilepsy, this case may represent an example of cocaine-induced kindling in humans.

Cocaine-related vascular headaches

The records of 21 patients admitted to hospital from January 1985 to December 1988 for acute headache associated with cocaine intoxication were reviewed. Fifteen patients were identified who experienced headaches with migrainous features in the absence of neurological or systemic complications. None of them had a history of cocaine-unrelated headaches or a family history of migraine, and all had a favourable outcome. Three possible mechanisms of cocaine-related vascular headaches are discussed which depend on the interval between cocaine ingestion and development of the headache. We postulate that acute headaches following cocaine use may relate to the sympathomimetic or vasoconstrictive effects of cocaine, while headaches following cocaine withdrawal or exacerbated during a cocaine "binge" may relate to cocaine-induced alteration of the serotoninergic system.

Hemiageusia: an unusual presentation of multiple sclerosis

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Displaced Torkildsen's shunt: an unusual cause of cervical myelopathy

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Transcranial magnetic stimulation in patients with epilepsy

We studied the effects of transcranial magnetic stimulation (TMS) applied in trains of 8- to 25-Hz stimuli on electroencephalographic epileptiform activity on eight patients being evaluated for epilepsy surgery. We performed the stimulation with a round water-cooled stimulation coil held flat on the scalp and centered over different positions of the International 10-20 System. We were unable to trigger seizures or induce epileptiform discharges arising from the epileptic focus in any of the eight patients with any of the stimulation protocols. However, we induced a partial motor seizure from the contralateral hemisphere to the exclusive temporal focus in the only patient stimulated with 100% maximal intensity. Precautions have to be taken when applying rapid TMS to patients because of the risk of seizure induction. Our results do not support the view that TMS specifically activates the epileptic foci.

Induction of speech arrest and counting errors with rapid-rate transcranial magnetic stimulation

Six adult epileptic patients underwent rapid-rate transcranial magnetic stimulation (rTMS) at stimulation rates of up to 25 Hz with an 11-cm water-cooled round coil held flat on the scalp, centered over 15 different positions on each side of the scalp. The trains of stimuli were for 10 seconds while the patients counted aloud. rTMS centered over D5 or D7 induced reproducible speech arrest in all patients and counting errors in three when applied at lower intensities. There were no such speech disturbances by rTMS centered over the different positions on the right side. Intracarotid amobarbital test (IAT) demonstrated left hemispheric language dominance in all patients. Lateralization of speech arrest induced by rTMS correlated with the IAT results and may be helpful for noninvasive determination of hemispheric language dominance.

Exacerbation of partial seizures and onset of nonepileptic myoclonus with carbamazepine

A child had two to three generalized tonic-clonic (GTC) seizures per week unresponsive to phenobarbital (PB) and valproate (VPA). Interictal EEG demonstrated left occipital spikes. When carbamazepine (CBZ) therapy was started, he developed very frequent (4-6/day) complex partial seizures (CPS) characterized on ictal EEG by focal right temporal lobe discharges. The seizure exacerbation, which was associated with development of nonepileptic, multifocal myoclonus, resolved 24 h after CBZ was discontinued. The exacerbation occurred with therapeutic CBZ serum levels, but may have been related to the toxic levels of carbamazepine-10, 11-epoxide (CBZE).

Cerebral atrophy in habitual cocaine abusers: a planimetric CT study

We compared cranial CTs of 35 habitual cocaine abusers, 16 self-reported 1st-time users, and 54 headache patients using linear planimetric measures. All patients met the following criteria: age 20 to 40 years, no polydrug abuse (including alcohol), HIV seronegativity, normal albumin level, and no history of any other neurologic disease. The sex ratios and ages were not significantly different in the 3 groups. The planimetric measurements and calculated indices of cerebral atrophy were significantly different in the habitual cocaine abusers compared with the 2 other groups of patients. There were no differences between 1st-time cocaine users and controls. Among the habitual cocaine abusers there was a positive correlation between the approximate duration of cocaine abuse and the calculated atrophy indices. The findings suggest that cerebral atrophy develops in chronic cocaine abusers, and the severity correlates with the duration of abuse.

EEG correlation of improvement in hemolytic-uremic syndrome after plasma infusion

We report a previously undescribed electroencephalographic pattern of epochs of diffuse delta background (85-240 sec) alternating with epochs of classic "burst suppression" (90-270 sec) in a 13-month-old girl with hemolytic-uremic syndrome. A dramatic electroencephalographic improvement was evident on continuous monitoring of cerebral function 3 hours after initiating fresh frozen plasma infusion, well before any clinical improvement was apparent. This patient, in addition to the unusual electroencephalographic findings, illustrates the role of continuous electrophysiologic monitoring of cerebral function and supports the use of fresh frozen plasma in hemolytic-uremic syndrome.

Cocaine-associated multifocal tics

Of 4 patients with cocaine-induced multifocal tics, 2 had Tourette's syndrome and had a severe exacerbation of their symptoms. One of these 2 patients experienced the exacerbation following her 1st exposure to the drug; the 2nd, a habitual cocaine snorter, after smoking "crack" for the 1st time. The other 2 patients were habitual cocaine abusers who, following a binge with high doses of cocaine, experienced new-onset tics.

Cocaine-induced seizures

We retrospectively studied 474 patients seen at Hennepin County Medical Center because of medical complications related to acute cocaine intoxication. Of the 474, 403 had no history of seizures. Seizures within 90 minutes of cocaine use was the primary diagnosis in 32 (7.9%) of the 403. The majority of seizures were single, generalized, induced by intravenous or "crack" cocaine, and not associated with any lasting neurologic deficits. Most that were focal, multiple, or induced by nasal cocaine were associated with an acute intracerebral complication or concurrent use of other drugs. Of 71 patients with a history of non-cocaine-related seizures, 12 (16.9%) presented with cocaine-induced seizures; most of these were multiple, of the same type as those in their history, and induced by even nasal cocaine. In the 44 cocaine-induced seizure patients, a pattern of habitual cocaine abuse was associated with diffuse brain atrophy on CT and diffuse slowing on EEG.

Volume therapy in orthostatic transient ischemic attacks

We report the case of an 83-year-old man with recurrent orthostatic transient ischemic attacks despite anticoagulation and crystalloid therapy. An initial cerebral angiogram revealed a nearly occluded right carotid artery with a string sign. Following aggressive volume expansion with albumin, the patient became asymptomatic. A second angiogram demonstrated the resolution of the carotid string sign and unmasked a high-grade, very tight, surgically approachable stenosis. The role of a high intravascular volume status is discussed.