15 - Pathophysiology of spontaneous cerebrospinal fluid leaks and their relationship with idiopathic intracranial hypertension

Abstract

In the past 3 decades, there has been increased recognition of the association between spontaneous skull base cerebrospinal fluid (CSF) leak and idiopathic intracranial hypertension (IIH). Patients with spontaneous CSF leak and those with IIH share similar demographic, clinical, and radiologic characteristics, and the incidence of both conditions has increased in recent years in parallel with the increasing rate of obesity. It is unclear whether spontaneous CSF leak represents a variant or advanced manifestation of IIH. The two conditions share a similar pathophysiology that involves venous and lymphatic drainage pathways, leading to intracranial hypertension. Other postulated mechanisms that lead to spontaneous CSF leak include an anatomic predisposition to thinning of the calvarium and skull base, particularly the cribriform plate and paranasal sinuses. This may be further exacerbated by transient spikes in intracranial pressure (ICP) and altered CSF dynamics that occur when sleep architecture is fragmented by obstructive sleep apnea, a highly prevalent comorbidity in patients with spontaneous CSF leak and IIH. This chapter reviews the evidence of a relationship between spontaneous CSF leak and IIH and discusses the proposed pathophysiology for spontaneous CSF leak in these patients, focusing on the shared demographic, clinical and radiologic features, and the evidence for alteration in CSF dynamics, dysregulation in cerebral venous pressure, anatomic predisposition to osseous thinning of the skull base, and the role of obstructive sleep apnea in the pathophysiology of spontaneous CSF leak.