Recognition of cerebrospinal fluid (CSF) leaks from the anterior or lateral skull base requires a high level of suspicion and a thorough examination to prevent potentially life-threatening sequelae. Blunt skull trauma, which disrupts the dural integrity and allows for CSF fistulization, accounts for 80% to 90% of CSF leaks. Patients with persistent CSF leaks have a 10% to 37% risk of developing meningitis, which carries a mortality rate of nearly 10%.¹ In cases of basilar skull fracture, epistaxis or hemotympanum may obscure the presence of clear fluid drainage from the nose or ear, making the diagnosis challenging. The temporal bone is involved in 18% to 40% of all skull fractures and may also contribute to a CSF leak.^2,3 Despite this noteworthy incidence, concomitant injuries usually associated with this diagnosis may distract providers’ attention. A thorough examination to identify injuries to nearby neurovascular structures (eg, facial nerve, internal carotid artery, internal jugular vein) and potential CSF leak is critical. In addition to trauma, CSF leaks may occur iatrogenically from surgeries of the sinus, skull base, or ear. Finally, although less common in the emergency setting, approximately 10% of patients suffer nontraumatic etiologies of CSF leaks, including those resulting from increased intracranial hypertension or sinonasal neoplasms.

A meticulous history often provides the key to elucidating the diagnosis and etiology of a CSF leak. Commonly, a patient with a CSF leak describes unilateral, clear rhinorrhea that worsens with bending forward or straining. This fluid is often described as being watery rather than having the consistency of mucus. Salty or metallic tasting nasopharyngeal drainage often accompanies these symptoms and persists despite topical steroid management, differentiating a CSF leak from chronic rhinitis or sinus disease. Iatrogenic CSF leaks are a rare but well-documented complication of endoscopic sinus surgery caused by occult skull base injuries. Iatrogenic leaks may present in a delayed fashion, so any historical account of sinus surgery, skull base surgery, or septoplasty should be considered a risk factor. Recurrent epistaxis, nasal obstruction, or constitutional symptoms (eg, fevers, night sweats, weight loss) may suggest a neoplasm involving the skull base. IIH may be considered in patients with known risk factors (eg, overweight females of childbearing age) and should be screened for by inquiring about headaches or vision changes prior to the onset of rhinorrhea.

It is imperative to consider a temporal bone fracture in any trauma to the head, particularly those with significant force, such as direct blows to the head from motor vehicle collisions, falls, and/or assaults. Studies suggest an increased proportion of temporal bone fractures caused by assaults versus motor vehicle collisions.^3,7 The force of the injury may be temporal or parietal (causing longitudinal fractures) versus frontal or occipital (resulting in transverse fractures). Hypacusis (total or significant hearing loss), tinnitus, balance problems, and vertigo are common complaints.¹⁰ In cases of blunt head trauma, altered patients may not be able to describe symptoms, which can lead to delay in the recognition of a CSF leak. In addition, epistaxis or hemotympanum from skull base fractures may obscure clear rhinorrhea or otorrhea (Table 21.1). In these instances, a high index of suspicion and radiographic imaging will be necessary to unmask a CSF fistula.