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An EEG is requested to determine the cause of clonic limb movements in an 8-day-old girl (gestational age¼ 39 weeks) who has bilateral intraventricular hemorrhages and herpetic encephali- tis. She is treated with phenobarbital, acyclovir, and antibiotics.

The technologist notes that the patient is occasionally arousable and mechanically ventilated. For a portion of the tracing not pictured, continuous activities of active sleep are recorded. These 30- and 10-second samples are taken 10 minutes before active sleep.

Questions: What is the ECA? Identify the activity state and accompanying background activity. Is background activity appropriate for the ECA? Of sharp transients markeda, b, or c, which are physiologic and which are pathologic?

Answers: The ECA is 40 1/7 weeks. The activity state and background activity are most consistent with quiet sleep and TD. Note that the breathing pattern is unreliably regular from mechanical ventilation. This activity is inappropriate for the ECA. Pathologic monophasic and polyphasic high-amplitude left temporal spikes and sharp waves (arrows a) and independent left central spikes and sharp waves of both negative and positive polarity (arrows b) occurred most frequently. Right temporal sharp waves and broader-based sharp transients and right central spikes also appear in the sample. Physiologic encoches frontales were also present (arrow c).

Discussion: Dysmaturity—the persistence of a pattern consistent with an earlier developmental stage—is an important abnormality in the neonatal tracing. The delayed persistence of a pattern of more than 2 weeks is a reasonable boundary beyond which a pattern should be considered dysmature. For example, continuous patterns are expected to emerge after ECA 28 weeks; therefore, the lack of continuous activities in a >30-week-old neonate implies encephalopathy. Similarly, the persistence of TD> ECA 36 weeks þ 2 weeks, as in the present case, is abnormal. Findings from the whole tracing, not just that con- fined to the previous sample, are required to distin- guish between persistent TD and suppression-burst. This case was interpreted as dysmature TD rather than suppression-burst because of continuous activities seen in the latter portion of the recording. Background activities provide the best prog- nostic information, but other abnormal findings help. Multifocal and frequent spikes, such as those shown in the current case, are abnormal.

Focal sharp waves and spikes present unique problems in neonatal tracings. Although spikes and sharp waves are defined with the same cri- teria among neonates, children, and adults, the types of epileptiform discharges and their signifi- cance differ.

Spikes seen in children and adults typically have negative potentials recorded at the scalp, whereas neonatal spikes may have positive potentials. Usu- ally, polarity of neonatal spikes has no special association with pathology. Two exceptions are Rolandic positive spikes (positive central sharp waves) and midtemporal positive spikes; these may be found in intraventricular hemorrhage. The present consensus, however, is that these dis- charges are not specific for hemorrhage but can also be present in other deep white matter lesions.

Another difference between spikes seen in neo- nates and those seen in older subjects is that the former are not specific to epilepsy. Neonatal spikes are a nonspecific indicator of focal pathol- ogy or diffuse encephalopathy.

Clinical Pearls

1. Persistent TD in the full-term infant is evidence of dysmaturity.

2. Spikes can be normal in the premature and full-term infant and are most evident within bursts of discontinuous background patterns.

3. Abnormal spikes tend to recur in trains, appear unilaterally, occur in between bursts of discontinuous patterns, and persist during continuous patterns.

4. Positive central and positive midtemporal sharp waves may indicate deep white matter lesions, but other pathologic spikes have more association with nonspecific diffuse or focal abnormalities and do not necessarily predict higher risk of subsequent seizures.

REFERENCES

1. Hahn J, Monyer H, Tharp B: Interburst interval measurements in the EEGs of premature infants with normal neurological outcome. Electroencephalogr Clin Neurophysiol 1989; 73:410–418.

2. Menache C, Bourgeois B, Volpe J: Prognostic value of neonatal discontinuous EEG. Pediatr Neurol 2002; 27:93–101. 3. Okumura A, Hayakawa F, Kato T, et al: Developmental outcome and types of chronic-stage EEG abnormalities in preterm

infants. Dev Med Child Neurol 2002; 44:729–734.

Spikes are commonly seen in normal neonates, especially during bursts of TD in the premature neonate and within quiet sleep and TA in full- term neonates. Frontal sharp transients (encoche frontale), for example, are normal despite their epileptiform morphology.

Unfortunately, no clear guidelines separate normal from abnormal spikes in neonates. Spikes

tend to be abnormal, if they occur in rhythmic runs, if they occur in one location only, if they recur within the low-amplitude portions of discontinuous patterns, if they persist through continuous background activities, or have a poly- phasic morphology. In this case, most spikes occurred within the high-amplitude bursts of TD, but others occurred in between.

PATIENT 31

A 7-year-old boy with nocturnal seizures

An EEG is requested in evaluation of nocturnal seizures that consisted of speech difficulties and right lower facial movements in a 7-year-old, otherwise healthy, boy whose father had childhood- onset seizures that resolved.

The patient takes no medications. Although awake in this segment, spikes were much more frequent with drowsiness (arrows). The sample is shown in both bipolar and referential montages.

Questions: What is the location of the negative-polarity spike discharges? What polarity (negative or positive) is displayed at electrode F3 (best seen at arrow a)? What epilepsy syndrome best fits the clinical description and electrographic findings?

FOCAL SHARP TRANSIENTS AND