Cerebrospinal fluid leak

Cerebrospinal fluid rhinorrhoea is caused by an abnormal connection between the subarachnoid space and the nose, either direct or indirect. Direct communication with the anterior cranial fossa occurs through the cribriform plate, ethmoid cells or frontal sinus, and with the middle cranial fossa through the sphenoid sinus. An indirect connection with the posterior fossa is possible via the eustachian tube and the otomastoid cavity.

Cerebrospinal fluid otorrhoea occurs in the presence of a tympanic membrane defect when the otomastoid cavity communicates with the posterior cranial fossa.

Most cerebrospinal fluid leaks are of traumatic origin. The most common fractures causing such a leak are ethmoid fractures (see facial fractures), but fractures in the frontal sinus, sphenoid sinus or temporal bone may also cause cerebrospinal fluid leakage. Spontaneous cerebrospinal fluid leaks may arise from an aberrant arachnoidal granulation or a congenital anomaly. Such congenital anomalies include a wide communication between the internal auditory canal and the inner ear structures, with leakage of cerebrospinal fluid into the middle ear.

Cerebrospinal fluid leak is also seen after surgery (Fig.1), and sometimes in tumoral pathology, encephaloceles or infection.

Depending on the clinical history, imaging should be directed to the facial skeleton or temporal bones. The presence of an airfluid level head and neck or opacified cell may give a clue to the location of the abnormal connection. Evidence of bone interruption should be searched for. Intrathecal injection of a contrast medium may help in identifying the leak.

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