Emergency Foramen Magnum Decompression for Tonsillar Herniation Secondary to Meningoencephalitis

Listeria meningitis associated with tonsillar herniation in an immunocompetent school-aged child

Listeria monocytogenes can cause severe illnesses such as gastroenteritis, sepsis and neurolisteriosis, especially in infants, the elderly and immunocompromised patients. We report a case of a previously healthy school-aged girl presenting with severe neurological deficits found to have Listeria meningoencephalitis. Her potential exposure to L. monocytogenes was consumption of contaminated cheese. She had some clinical improvement after initiation of tailored Listeria anti-microbial coverage with ampicillin and gentamicin; however, she developed hydrocephalus requiring external ventricular drain placement and tonsillar herniation requiring emergent posterior fossa decompression. The patient made significant improvements after neurosurgical intervention, and along with continued antibiotics and subsequent rehabilitation services, she improved to near full recovery within a year. The case highlights that neurolisteriosis can affect even immunocompetent children, and aggressive neurosurgical interventions should be considered in patients who develop severe complications such as hydrocephalus and tonsillar herniation to improve outcomes.

The Chiari I malformation

As with many pathologies, the course of our understanding of the Chiari I malformation (CIM) has developed extensively over time. The early descriptions of the Chiari malformations by Hans Chiari in 1891 opened the door for future classification and research on this topic. However, even over a long timeframe, our understanding of the pathophysiology and, more importantly, treatment, remained in its infancy. As recently as the 1970s, CIM was not discussed in popular neurology textbooks. Syringomyelia is listed as a degenerative disorder with no satisfactory treatment. Radiation therapy was considered an option in treatment, and surgery was thought to play no role. During the last 40 years, equivalent to the duration of a neurosurgical career, our understanding of the pathophysiology and natural history of CIM, coupled with modern MRI, has improved the treatment paradigm for this patient population. More importantly, it has given us evidence confirming that CIM is a disorder responsive to surgical intervention, giving patients once thought to be destined for lifelong disability a comparatively normal life after treatment. The purpose of this article is to offer a review of CIM and its important associated entities. The authors will discuss the evolution in understanding of the Chiari malformation and, importantly, distinguish between symptomatic CIM and asymptomatic tonsillar ectopia, based on imaging and presenting symptomatology. They will discuss techniques for surgical intervention, expected outcomes, and complications after surgery. Proper patient selection for surgery based on appropriate symptomatology is tantamount to achieving good surgical outcomes in this population, separating those who can be helped by surgery from those who are unlikely to improve. While our knowledge of the Chiari malformations continues to improve through the efforts of clinical and basic science researchers, surgeons, and patients, our current understanding of these entities represents a monumental improvement in patient care over a relatively short time period.