Neurology Residency Program Director, Assistant Professor of Neurology (Interim), Weill Cornell Medical College and NewYork-Presbyterian Hospital

Dr. Robbins reports no financial relationships relevant to this field of study.

SYNOPSIS: Clinical features of patients with spontaneous intracranial hypotension and bilateral subdural fluid collections differ from patients who sustained previous head trauma vs. those with cerebrospinal fluid leaks.

SOURCE: Kim JH, Roh H, Yoon WK, et al. Clinical features of patients with spontaneous intracranial hypotension complicated with bilateral subdural fluid collections. Headache 2019;59:775-786.

Subdural fluid collections are a radiographic finding in patients who have both spontaneous intracranial hypotension (SIH) and other causes, most notably head trauma. Subdural fluid collections may progress to or evolve from chronic subdural hematomas. Distinguishing between etiologies is critical to ensure that such patients receive the correct diagnosis and treatment.

Kim et al performed a single-center, retrospective study of all patients presenting to their center in Korea with symptomatic, bilateral subdural fluid collections. They excluded any patients with prior neurosurgical intervention or acute subdural hematomas. They stratified their sample into two groups: one group fulfilled the International Classification of Headache Disorders, 3rd edition, diagnostic criteria for headache attributed to SIH, and the other group did not fulfill these criteria. Then, the authors compared clinical, radiological, and outcome data.

The authors’ final dataset included 62 patients with bilateral symptomatic subdural fluid collections, among whom eight patients (13%) had SIH. SIH patients were significantly different from non-SIH patients, including younger age (odds ratio [OR], 0.831; 95% confidence interval [CI], 0.743-0.929; P = 0.0012) and fewer medical comorbidities (OR, 0.062; 95% CI, 0.007-0.544; P = 0.0121). On neuroimaging, patients with SIH were more likely to feature brain sagging (OR, 10.36; 95% CI, 0.912-93.411; P = 0.0017), pseudo-subarachnoid hemorrhage (OR, 15.6; 95% CI, 2.088-116.52; P = 0.0074), and smaller subdural fluid collections (OR, 0.719; 95% CI, 0.579-0.893; P = 0.0029). A more detailed analysis using receiver-operator characteristics yielded cutoffs of age (≤ 55 years) and total depth of subdural fluid collections (≤ 22.08 mm).

Among the eight patients with SIH, four had orthostatic headache. Three patients had pseudo-subarachnoid hemorrhage on initial CT imaging. Cerebrospinal fluid (CSF) leak sources included nerve root sleeves (5), CSF-venous fistulas (2), and a ventral dural tear (1). Most patients underwent targeted (4) or non-targeted lumbar (3) epidural blood patches, and one patient had neurosurgical drainage, did poorly, and was the subject of a separate case report. The authors concluded that bilateral subdural fluid collections associated with SIH were more likely to feature a younger age, fewer comorbidities, smaller size of subdural fluid collections, and imaging suggestive of brain sagging or pseudo-subarachnoid hemorrhage.

COMMENTARY

SIH is a disorder featuring low CSF pressure or volume typically secondary to a CSF leak in the spine. Although it is not a common disorder, increasingly it has been recognized as an important diagnostic consideration of the syndrome of new daily persistent headache (which itself may have up to a 0.1% population prevalence) and is highly disabling. Myriad radiological findings related to the loss of brain buoyancy and venous engorgement, including but not limited to diffuse, smooth, pachymeningeal enhancement, often are diagnostic. However, many patients have more subtle brain or spine abnormalities or only may have unenhanced CT imaging where subdural fluid collections are noted.

The presentation of patients who typically have headache accompanied by the finding of bilateral subdural fluid collections, or hygromas, is an occasional reason for neurological or neurosurgical consultation on an inpatient or outpatient basis. The authors divided the etiologies into SIH and non-SIH causes, which typically include traumatic head injury or spontaneous collections that develop in the setting of anticoagulant or antiplatelet agent use. Although the clinical features distinguishing between the causes may be intuitive to some neurologists, such patients initially present to the emergency department, where rapid treatment decisions need to be made, particularly regarding any neurosurgical intervention.

A proper diagnosis in this patient population requires a detailed history. Patients with SIH often have an orthostatic, new, daily persistent, exertional, or “second half of the day” headache, but auditory and vestibular symptoms also are extremely common. Patients with bilateral subdural collections from other etiologies typically are older, have had closed head trauma or a recent fall, or are taking medications that increase the risk of bleeding. They also may be entirely asymptomatic and the collections, often labeled as hygromas, may be incidental findings or the sequelae of previous subdural hemorrhage.

Neurosurgical drainage of subdural collections or hematomas when the etiology is SIH may lead to clinical deterioration in some patients, so diagnostic clarity remains critical in ensuring effective and safe treatment. An area that needs further exploration is the clinical presentation of patients with SIH, with and without subdural fluid collections. It is reasonable to hypothesize that subdural fluid collections could become space-occupying lesions themselves and change the expression of headache in patients with SIH.