Grand Rounds

Not All Seizures Are Epileptic: A Neonatal Case of Hyperekplexia

Catarina Fraga¹, Ana Azevedo², Sérgia Soares¹, Catarina Viveiros^2
1Pediatrics Department, Hospital Pedro Hispano, Unidade Local de Saúde de Matosinhos, Oporto, Portugal, ²Neonatology Unit, Hospital Pedro Hispano, Unidade Local de Saúde de Matosinhos, Oporto, Portugal

Address for Correspondence: Catarina Fraga, Rua Eduardo Torres 4464-513 Senhora da Hora, Portugal Email: catarinafragapediatra@gmail.com

Keywords: Hyperekplexia, Startle Syndrome, Hypertonia

Clinical Problem:
A full-term male newborn was delivered via vacuum extraction to non-consanguineous parents following a monitored pregnancy. He presented risk factors for infection, including maternal colonisation of group B Streptococcus and a urinary tract infection during the third trimester. A few hours after birth, he developed generalised hypertonia, feeding difficulties, abnormal posturing - including chewing-like movements and marked cervical hyperextension. Although these symptoms were initially suspected to be neonatal seizures, they did not respond to prompt treatment with phenobarbital and levetiracetam.
The newborn was transferred to a Neonatal Intensive Care Unit (NICU) where he remained stable but continued to exhibit the same findings. He displayed exaggerated startle reflexes triggered by minimal stimuli, preserved consciousness, and sleep-specific myoclonus. While the EEG was not available, other causes such as infections, structural anomalies and metabolic disorders were discarded. Then, an EEG was performed and revealed episodes of startle without epileptiform activity. A clinical diagnosis of hyperekplexia was considered, and clonazepam was initiated, providing relief from the symptoms. However, occasional Vigevano manoeuvres were required to manage episodes of hypertonia.

What clinical features and investigations enable clinicians to reliably distinguish neonatal hyperekplexia from seizures and other causes of neonatal hypertonia, and how does this distinction influence immediate management strategies?