CSF rhinorrhea is the drainage of the fluid which surrounds the brain into the nose (CSF =cerebral spinal fluid + rhinorrhea = fluid draining from the nose).
The choroid plexus of lateral ventricles of the brain produces approximately 800mililiters of cerebral spinal fluid daily. This clear fluid leaves the brain through the third ventricle to the fourth ventricle, and then into the subarachnoid space that surrounds the brain and spinal cord. The CSF is absorbed by a highly specialized finger-like extension of the arachnoidnoidal membrane surrounding the brain, known as the arachnoid villi. This so called "brain fluid" has the important functions of cushioning the brain, maintaining pressure within the eye, and cleansing the central nervous system much like the lymphatic system serves the same function in the rest of the body.
A breach in dura (the periosteal or nutrient membrane lining the inside of the skull) over or adjacent to the nose, sinuses or ear can provide a pathway for CSF to drain from the subarachnoid space into the nose. In such cases, an individual may first become aware of this serious event by the drainage of clear fluid from the nose or the perception of a salty fluid draining from the nose into the throat. CSF rhinorrhea can be the result of trauma to head, nasal or ear surgery or occur spontaneously.
Patients may have CSF rhinorrhea for years without having any undo consequences. Others may develop bacterial meningitis within days of the onset of the rhinorrhea because in both situations an open communication exists between the brain cavity and the non-sterile nose.
Obviously, CSF rhinorrhea requires medical attention and any change in the individual's level of consciousness, fever, chills or stiff neck implies meningitis. As bacterial meningitis can be fatal and survival is dependent on rapid treatment, such inflicted individuals must seek immediate medical care. In doing so, communicating a history of CSF will assist the treating physicians in arriving at the right diagnosis and appropriate treatment. Fortunately, most clear drainage from the nose is not CSF and often reflects such conditions as allergy.
Coronal cadaver section illustrating potential sites of CSF rhinorrhea. A breach in the anterior cranial fossa floor (ACF) or middle cranial fossa floor provides a route for drainage of CSF to the nose. These routes include via the posterior wall of the frontal sinus (FS), roof of the ethmoid sinus (ES), sphenoid sinus (SS), and middle cranial fossa through the roof of the middle and inner ear to the eustachian tube (ET) to the nasopharynx (the space behind the nose which communicates with the throat).
Diagnosis of Cerebrospinal Fluid Rhinorrhea
As is true of the diagnosis of all human disease, a careful history and physical examination is essential. The history should include events associated with the onset of rhinorrhea, such as prior surgery or trauma; the character of the nasal drainage, watery or mucus-like; duration of the rhinorrhea; what makes the rhinorrhea better and worse; potential complications, such as meningitis; and, prior treatment.
The physical examination should include a comprehensive survey of the head and neck; endoscopy of the nasal cavity and adjacent regions, such as the osteomeatal complex and eustachian tube orifice which can be sites of CSF drainage; and, positioning the patient to observe and collect the nasal drainage.
Analysis of the collected nasal fluid can be both problematic and useful. Analysis of nasal fluid is problematic because simple testing such as observing how the drainage dries on paper (known as a ring sign) or measuring the sugar content (reflecting the elevated glucose content of CSF) may not be valid (Dula, 1993). Whereas, the presence of the enzyme Î²2-transferrinase is only found in CSF, but requires the collection of several milliliters of fluid to be sent for highly specialized laboratory testing (Irajala, 1979).
To confirm or further identify the route of CSF rhinorrhea, three forms of imaging are available. The most sensitive, but least specific form of imaging is an isotope cisternogram. This nuclear medicine study consists of placing a low yield radioactive isotope in the subarachnoid space via a lumber puncture or spinal tap. The presence of isotope containing CSF in the nose is confirmed by measuring radioactivity within the nasal cavity or on cotton pledgets placed at probable sites of cerebral spinal fluid drainage from the cranial cavity.
Contrast CT cisternography is a more specific, but a less sensitive form of imaging for CSF rhinorrhea. This radiographic study requires an active leakage of CSF to the nose and involves the placement of an agent opaque to CT imaging within the subarachnoid space (Schaefer, 1980). A coronal CT scan is then performed to image the defect within the floor of the anterior or middle cranial fossa, and the route of drainage into the nose (Eljamel, 1995).
The third form of imaging is magnetic resonance (MR). MR imaging is a non-radiographic procedure utilizing the detection of electromagnetic energy released from the hydrogen atom as the electron circling the nucleus descends to a lower energy level. As soft tissue contains various amounts of water and the physics of detecting changes in energy rather than density (as in the case of CT) significantly favor the former.
Therefore, MR imaging is the examination of choice for visualizing potential brain anomalies, such as encephaloceles (herniation of brain into the nose or ear). MR also permits the identification of CSF draining into the nose without the use of contract, but does not visualize well bony detect in the skull base or currently lacks the detail provided by CT cisternography.
Coronal CT cisternogram showing CSF draining from the subarachnoid space through the roof of the right ethmoid sinus (arrow) into the nose.
Coronal CT of a patient present with CSF rhinorrhea after ethmoid surgery. This non-contrast study shows a defect in the floor of the right ethmoid sinus and possible soft tissue or brain, filling this site (arrow)
Coronal MRI of the patient on the left showing an encephalocele and CSF draining into the roof of the right ethmoid sinus (arrow). CSF is also visible as pooling within the maxillary sinus (MS).
The surgical treatment of CSF rhinorrhea has evolved from purely an external procedure utilizing a craniotomy to visualize the floor of the anterior or middle cranial fossa to a range of intranasal endoscopic, external ethmoidectomy, middle ear and variations of craniotomy approaches. Each approach has inherent advantages, indications and is employed depending on the experience of the surgeon. Over the past twenty-five years, we have evolved the use of intranasl microscopic and more recently, endoscopic approaches to repair CSF rhinorrhea secondary to fistulas to the nose and sinuses (Bachert, 2000; Senior, 2001).
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