Abstract

Background:Chiari malformation type 1 (CM1) is a common congenital anomaly of the craniocervical junction. CM1 is reported to run a usually benign course and patients typically experience no symptoms or chronic, slowly progressive symptoms. However, recent reports indicate that a subset of patients with CM1 may present with acute deterioration and sudden unexpected death (SUD). We report a case of SUD during sleep in a young man with CM1, which we believe was related to the administration of common and therapeutic doses of narcotic analgesics for the management of pain. We will clarify the pathophysiology of acute deterioration and SUD in CM1 and the possibility that the adverse effects of opiate analgesics likely were the leading cause of death in our patient.

Case Description:In this review, we present a 29-year-old male with worsening headache secondary to previously diagnosed CM1. The patient died suddenly and unexpectedly after administration of common and therapeutic doses of narcotic analgesics for the management of pain.

Conclusion:The mechanism(s) of acute neurological deterioration and sudden death in patients with CM1 remains poorly understood. We believe the rapid fatal deterioration in our patient following administration of opioids suggests that this category of medication may cause sudden unexpected “neurogenic” cardiac death in CM1 patients by inducing sleep-related breathing difficulties and associated hypercapnia. Hypercapnia by further increasing intracranial pressure can result in a sudden pressure-induced decompensation of the cardiopulmonary control centers in the brain stem and cause instantaneous cardiorespiratory arrest.

At the center of this paper is the question about what exactly is Chiari malformation. It was first described by a pathologist who observed the descent of the cerebellar tonsils in cadavers of individuals with myelomeningocele. Hence, Chiari malformation was for long associated with spina bifida. In the 1938 Penfield[1] described the case of a young woman who could not wink whom he operated under the presumptive diagnosis of CP angle tumor. Penfield observed that the tonsils were descended; as the patient had a thoracic meningocele Penfield linked both conditions. In the following years, other papers[2] described the descent of the cerebellar tonsils in individuals without any form of spina bifida. For many, the etiology is a disproportion between the cerebellar volume and that of the posterior fossa, nonetheless along the years other alternatives have been presented. I recommend reading Milrohat.[3] Nowadays it is fair to say that we are in a position to defend our opinion about what we believe is the etiology of the descended tonsils, but we are not remotely near of understanding the pathophysiology of the gamut of symptoms that we, correctly or not, have attributed to the descend of the cerebellar tonsils. The question raised by any clinical paper on Chiari is: are descended cerebellar tonsils sufficient for diagnosing Chiari or we need some symptoms associated to the finding? How shall we weight the symptoms and the imaging? This question posed in the real world of our daily practice, not on the ideal world of the bureaucrats. Nowadays we order brain MRI for a simple headache. So when the patient comes with headaches, not necessarily provoked by a Valsalva, but has evidence of Chiari malformation, do we proceed and decompress? Do we act to preempt the possibility of more severe consequences? Are headaches just the beginning of a process such as we believe colon polyps are? Or, headaches do not “progress” into something more ominous as described in this paper. How can we define the many subsets of Chiari patients that while having identical MRI have a different clinical picture? The answer to this question will come through a thorough epistemological inquiry about causality.