Elsevier

The Lancet Neurology

Volume 21, Issue 4, April 2022, Pages 369-380
The Lancet Neurology

Review
Spontaneous intracranial hypotension: searching for the CSF leak

https://doi.org/10.1016/S1474-4422(21)00423-3Get rights and content

Summary

Spontaneous intracranial hypotension is caused by loss of CSF at the level of the spine. The most frequent symptom of this disorder is orthostatic headache, with the headache worsening in the upright position and subsiding after lying down. Neuroimaging has a crucial role in diagnosing and monitoring spontaneous intracranial hypotension, because it provides objective (albeit often subtle) data despite the variable clinical syndromes and often normal lumbar puncture opening pressure associated with this disorder. Spine imaging aims to classify and localise the site of CSF leakage as either (1) a ventral dural leak, (2) a leaking spinal nerve root diverticulum, or (3) a direct CSF-venous fistula. Searching for a CSF leak can be very difficult; the entire spine must be scrutinised for a dural breach often the size of a pin. Precisely locating the site of CSF leakage is fundamental to successful treatment, which includes a targeted epidural patch and surgical closure when conservative measures do not provide long-term relief. Increased awareness of spontaneous intracranial hypotension among clinicians highlights the need for dedicated diagnostic and therapeutic guidelines.

Introduction

Spontaneous intracranial hypotension is a debilitating medical condition caused by loss of CSF from the spinal canal. Despite not typically being considered a serious or life-threatening disorder, spontaneous intracranial hypotension can cause considerable morbidity, result in substantial long-term disability, and (in rare cases) lead to decreased consciousness and coma.1, 2, 3

Our knowledge about spontaneous intracranial hypotension has substantially increased over the past decade, and the underlying pathological mechanisms of this disorder have been elucidated. Nonetheless, diagnostic criteria for spontaneous intracranial hypotension, and the optimal assessments to use, remain topics for debate. For example, according to the International Classification of Headache Disorders (ICHD-3), either a low opening pressure on lumbar puncture (<6 cm CSF) or typical radiological signs of intracranial hypotension (either direct on spine imaging or indirect on brain imaging) are required for a diagnosis of spontaneous intracranial hypotension.4 Low opening pressure is, however, an unreliable marker of the disorder because it has been reported in only a third of patients with confirmed spontaneous intracranial hypotension.5, 6 Neuroimaging is, therefore, a more reliable method for the diagnosis of individuals with suspected spontaneous intracranial hypotension. As such, clinicians and radiologists need to be familiar not only with the typical findings of spontaneous intracranial hypotension that are seen on brain and spine imaging but also with the strengths and weaknesses of the various imaging methods that could be used for management of the patient at each stage of this condition.

In this Review, we provide an update on spontaneous intracranial hypotension and its management. We describe the use of brain MRI and spinal assessments for localisation of CSF leaks and highlight the challenges that might be encountered. Finally, we evaluate a three-tier therapeutic consensus approach with increasing levels of invasiveness that has been proposed for spontaneous intracranial hypotension.

Section snippets

Epidemiology and clinical presentation

The estimated incidence of spontaneous intracranial hypotension is five cases per 100 000 person-years, although growing recognition among health-care practitioners, and increased sensitivity of diagnostic tests, points to a higher true incidence.7, 8 Women are more often affected than are men, with a female to male ratio of approximately 2:1.

Most patients with spontaneous intracranial hypotension present acutely with typical orthostatic headache. The headache intensifies in the upright

Causes and risk factors

There are three types of CSF leak (figure 1). Type 1 leaks are typically ventrally located dural slits caused by an osteodiscogenic microspur (eg, a calcified disc protrusion or osteophyte [vertebral outgrowth]) penetrating the thecal sac. Type 2 leaks are leaking spinal nerve root diverticula. Type 3 leaks are direct CSF-venous fistulas.16 Type 1 and 2 leaks typically lead to CSF effusion from the intrathecal space to the epidural compartment, resulting in a spinal longitudinal extradural CSF

Associated morbidity

Evidence is increasing to support associations between spontaneous intracranial hypotension and other morbidities that previously were not thought to be linked. For example, intracranial hypotension can lead to the formation of subdural haematomas, which are most likely to be caused by injury to bridging veins that have been stretched by the sagging brain.23 Although decompressive craniotomy might be required for patients with severe haematomas, surgery will not treat the underlying cause, and

Diagnosis

A careful diagnostic evaluation of patients who are clinically suspected to have spontaneous intracranial hypotension is crucial, with awareness that imaging abnormalities are central to the ICHD-3 criteria (appendix p 2). Available diagnostic tools can be categorised according to degree of invasiveness (non-invasive vs invasive), imaging method (MRI, CT, fluoroscopy, or ultrasound), and whether the study provides direct (spine) or indirect (brain, optic nerve, or renal pelvis opacification)

Treatment

Patients with spontaneous intracranial hypotension should be treated in a multidisciplinary setting by neurologists, neuroradiologists, and neurosurgeons. A three-tier therapeutic consensus approach is followed for treatment of patients with spontaneous intracranial hypotension, with an increasing level of invasiveness and reliance on precise leak localisation. This approach includes—in order of increasing invasiveness—conservative treatment (bed rest or caffeine), percutaneous treatment with

Conclusions and future directions

Awareness of spontaneous intracranial hypotension is growing amongst neurologists, neuroradiologists, and neurosurgeons. The most common symptom of this disorder is orthostatic headache, but a myriad of clinical and radiographic presentations are possible and can lead to considerable diagnostic delay and psychological burden. Despite the widely recognised name of the syndrome, CSF hypotension is not a reliable marker of spontaneous intracranial hypotension. A rational and meticulous evaluation

Search strategy and selection criteria

We searched PubMed, MEDLINE, PsycInfo, and Embase databases for papers published between Jan 1, 2014, and Jan 1, 2021, using the terms “spontaneous intracranial hypotension”, “CSF leak”, “CSF loss”, and “CSF venous fistula”. We imposed no language restrictions. We also identified articles through citations and reference lists, review articles, and the authors' own publications. The final reference list was generated on the basis of the relevance of papers to the topics that are discussed in

Declaration of interests

We declare no competing interests.

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