Neonatal herpes simplex meningoencephalitis: EEG investigations and clinical correlates.

We studied the sequential EEGs of 15 neonatal herpes simplex virus meningoencephalitis (NHSV-ME) patients and correlated them with corresponding clinical and laboratory findings. During days 1 to 4 of the illness, 8 had EEGs. All but 1 had abnormal tracings and 3 (38%) showed the multifocal periodic pattern (MPP). Three had an early abnormal EEG at a time when their cranial CT/ultrasound studies were normal. During days 5 to 11, 13 had EEGs: all were abnormal and 3 showed the MPP. After day 11, EEGs (available on 10) showed a very low voltage background in 9, and only 1 had normal EEG and development. During 1 year in which 1 patient with NHSV-ME was observed, we noted that 9/324 (2.8%) of neonates with other CNS conditions manifested the MPP. All, however, had CSF findings that distinguished them from herpes cases. We conclude that: (1) In patients with suspected NHSV-ME, EEG is a sensitive test that is superior to radiologic procedures in detecting early cerebral involvement. Most of the early EEGs show nonspecific background and paroxysmal abnormalities. (2) In the presence of inflammatory CSF, the MPP, an otherwise nonspecific finding, is highly suggestive of NHSV-ME. (3) Sequential EEGs may be important in the follow-up of neonates with NHSV-ME.