Tonsillar herniation and coning is a rare and often late presentation of meningoencephalitis, and is associated with poor neurological outcome. We report the case of a 16-year-old female who presented unresponsive with radiological evidence of tonsillar herniation secondary to meningoencephalitis. She underwent an emergency foramen magnum decompression and C1 laminectomy with full recovery and no residual neurological deficit.

Tonsillar herniation and coning is a rare complication of meningoencephalitis and is associated with poor neurological outcome. Our patient presented unresponsive with radiological evidence of tonsillar herniation secondary to meningoencephalitis. She underwent an emergency foramen magnum decompression and C1 laminectomy with full recovery.16 years old female presented to her local ED with headache, vomiting, hallucinations, photophobia and neck stiffness. Her CT head was normal. She was commenced on acyclovir and ceftriaxone on the same day and clinically improved. LP performed 24 hours later showed WBC of 226 (200 lymphocytes, 6 polymorphs), protein 1.2 g/L, negative MC and S, negative viral PCR, negative TB PCR. CSF glucose was not sent. In light of a predominantly lymphocytic CSF and presumed viral meningitis antibiotics were stopped. Three days later acutely deteriorated. MRI head showed evidence of tonsillar herniation. She was restarted on antibiotics and was transferred to tertiary centre. She underwent emergency insertion of an EVD, foramen magnum decompression and C1 arch laminectomy. She made a full recovery with no residual neurological deficit.The mainstay treatment of meningoenecephalitis is intravenous antibiotics. However, in cases complicated by tonsillar herniation with reactive pupils, foramen magnum decompression should be considered.