bubble_chart Overview

Cerebrospinal fluid otorrhea is often caused by fractures of the middle cranial fossa involving the tympanic cavity. Since the petrous bone is located at the junction of the middle and posterior cranial fossae, fractures in either the middle or posterior fossa portion of the petrous bone can result in bloody cerebrospinal fluid entering the tympanic cavity if the middle ear cavity is injured. If the tympanic membrane is ruptured, the fluid may drain through the external auditory canal. If the tympanic membrane is intact, the cerebrospinal fluid may flow through the Eustachian tube to the pharynx or even reflux through the choanae into the nasal cavity and out the nostrils, mimicking the nasal fistula caused by anterior fossa fractures, which can easily lead to misdiagnosis and warrants attention. Petrous bone fractures often involve injuries to the facial and auditory nerves, with incidence rates of 19.8% and 31.4%, respectively. Occasionally, the abducens or trigeminal nerves may also be injured. Additionally, delayed subcutaneous ecchymosis in the postauricular mastoid region (Battle’s sign) is a common indicator of temporal petrous bone fractures. Cerebrospinal fluid wound fistulas (cutaneous fistulas) are almost always caused by improper initial management of open craniocerebral injuries, particularly in cases of penetrating gunshot wounds, where inadequate repair of the dura mater or poor wound healing due to infection leads to leakage. If the cerebrospinal fluid fistula originates directly from a penetrating ventricular injury, significant fluid loss can occur, leading not only to systemic deterioration but also to severe meningitis and encephalitis, especially in pediatric patients, necessitating prompt debridement and repair. Cerebrospinal fluid leakage through the nasal cavity, ear canal, or open wounds is a serious complication of craniocerebral injuries and can lead to intracranial infection, with an incidence rate of approximately 2–9% (MacGee et al., 1970). Cerebrospinal fluid fistulas occur when a skull fracture simultaneously tears the dura mater and arachnoid membrane, allowing cerebrospinal fluid to escape through the fracture line into the nasal cavity, external auditory canal, or open wound, creating a communication between the cranial cavity and the external environment. This forms a fistula, while air may also enter retrogradely, leading to pneumocephalus.

bubble_chart Clinical Manifestations

Cerebrospinal fluid nasal fistula disease is commonly seen in anterior cranial fossa fractures, with an incidence as high as 39% (Ray & Bergland, 1969). In acute sexually transmitted disease patients, bloody fluid often leaks from the nasal cavity after injury, accompanied by subcutaneous static blood in the orbital region (commonly known as "raccoon eyes") and subconjunctival membrane hemorrhage. This may be associated with loss or reduction of the sense of smell, and occasionally, injury to the optic or oculomotor nerves. Delayed cerebrospinal fluid nasal fistula disease often occurs after an anterior cranial fossa fracture, varying in duration, when a sudden cough or exertion causes a sharp increase in intracranial pressure, leading to the rupture of the cerebral membrane and the formation of a fistula. The discharged fluid is clear cerebrospinal fluid. Generally, the fistula discharge increases when the patient sits up or lowers their head and stops when lying flat, as the fluid flows toward the posterior nasal aperture and is swallowed or accumulates in the sphenoid sinus and other paranasal sinus cavities. Therefore, such patients often experience more leakage upon waking up in the morning.

Cerebrospinal fluid ear fistula disease is often caused by middle cranial fossa fractures involving the tympanic cavity. Since the petrous bone is located at the junction of the middle and posterior cranial fossae, fractures in either the middle or posterior fossa portion of the petrous bone can lead to bloody cerebrospinal fluid entering the tympanic cavity if the middle ear cavity is injured. If the tympanic membrane is ruptured, the fluid leaks through the external auditory canal. If the tympanic membrane is intact, the cerebrospinal fluid may flow through the Eustachian tube to the pharynx or even reflux from the posterior nasal aperture to the nasal cavity, mimicking a nasal fistula caused by an anterior fossa fracture, which can easily lead to misdiagnosis and requires attention. Petrous bone fractures are often accompanied by facial and auditory nerve injuries, with incidence rates of 19.8% and 31.4%, respectively, and occasionally may cause abducens or trigeminal nerve injuries. Additionally, delayed subcutaneous ecchymosis in the postauricular mastoid region (Battle's sign) is also a common sign of temporal petrous bone fractures.

Cerebrospinal fluid wound fistula disease (cutaneous fistula disease) is almost always caused by improper initial [first stage] management of open craniocerebral injuries, commonly seen in penetrating gunshot wounds to the brain, due to inadequate repair of the dura mater or poor wound healing caused by infection. If the cerebrospinal fluid fistula directly results from a ventricular penetrating injury, a large amount of cerebrospinal fluid may be lost, leading not only to systemic deterioration but also often to severe meningitis and encephalitis, especially in pediatric patients, necessitating timely debridement and repair.

bubble_chart Diagnosis

The diagnosis of cerebrospinal fluid fistula disease first involves determining the nature of the discharge. Since cerebrospinal fluid has a high sugar content, it can be measured using "urine glucose test strips." Sometimes, the discharge from fistula disease is mixed with blood, making biochemical assays difficult for definitive diagnosis. In such cases, the red blood cell count method can be employed by comparing the blood cell counts of the fistula fluid and blood to make a judgment. However, a definitive diagnosis still relies on specialized examination methods: - Skull X-ray plain films can reveal whether there is a fracture crossing the paranasal sinuses or petrous bone. - CT scans help detect the presence of pneumocephalus and, through window level adjustments, observe skull base fractures. - Radionuclide cisternography can be performed by injecting ¹³¹I-labeled human serum albumin (HISA), 99mT_c, or 169Y_b-DTPA into the subarachnoid space via lumbar puncture for cisternography to locate the fistula site. Alternatively, a water-soluble contrast agent (Metrizamide) can be injected into the subarachnoid space. Under fluoroscopy, the patient's position is adjusted to allow the contrast agent to enter the basal cisterns, followed by thin-section CT scanning of the skull base to visualize the fistula site.

bubble_chart Treatment Measures

Acute cerebrospinal fluid nasal fistula or ear fistula disease caused by skull base fracture can mostly be cured through non-surgical treatment. Only a few cases that persist for more than 3–4 weeks without healing require surgical intervention.

I. Non-surgical treatment: Generally, the patient is positioned with the head elevated at 30° and lying on the affected side, allowing the brain tissue to settle over the fistula site to facilitate adhesion and healing. Concurrently, the nasal cavity or ear canal should be kept clean, avoiding nose-blowing, coughing, and straining. Bowel movements should be kept regular, fluid intake should be restricted, and medications to reduce cerebrospinal fluid secretion, such as acetazolamide (Diamox), or mannitol for diuresis and dehydration, may be administered. If necessary, lumbar puncture for cerebrospinal fluid drainage can be performed to reduce or stop fistula leakage, aiding the healing of the fistula. Approximately 85% or more of patients with cerebrospinal fluid nasal or ear fistula recover after 1–2 weeks of conservative treatment.

II. Surgical treatment: Only about 2.4% of traumatic cerebrospinal fluid fistulas require surgical intervention. Surgery is considered only when the fistula fails to heal or recurs multiple times after spontaneous healing.

1. Cerebrospinal fluid nasal fistula repair: Preoperative localization of the fistula is essential, as described above. Once the fistula site is identified, a craniotomy via a unilateral or bilateral frontal bone flap is performed. Initial exploration is conducted extradurally, carefully separating the dura from the posterior wall of the frontal sinus, orbital roof, sphenoid ridge, or cribriform plate based on the suspected location. The fistula site is often marked by thickened dura that has herniated into the fracture line. The dura should be dissected close to the skull to avoid enlarging the fistula. Soft tissue around the skull defect is cauterized and pushed into the fracture line; if it involves a sinus wall, it is pushed into the sinus cavity, and the skull defect is sealed with bone wax or medical adhesive. The dural defect is then tightly sutured or repaired, typically using temporal fascia, periosteum, or galea aponeurotica as graft material to ensure a watertight closure. For larger fistulas or if extradural exploration is difficult, the dura may be incised in a flap to elevate the frontal lobe and directly inspect the anterior skull base for the fistula. Fistulas are commonly located in the cribriform plate, posterior wall of the frontal sinus, sella turcica, or parasellar region, and occasionally in the greater wing of the sphenoid bone due to excessive pneumatization. At the fistula site, the arachnoid and brain tissue often protrude, with local adhesions, gliosis, and sometimes inflammatory granulation tissue or abscess formation. After isolating the area, the adherent brain tissue is gently separated and lifted, and the inflammatory tissue at the fistula is curetted and cauterized. Small fistulas may be plugged with muscle fragments soaked in medical adhesive, followed by overlaying with available dura, falx cerebri, periosteum, temporal fascia, or galea aponeurotica, which is then tightly sutured or secured with adhesive. For larger skull base defects, combined intra- and extradural exploration may be necessary to determine the repair strategy. Typically, the dural defect is patched from the inside with tissue grafts, followed by reinforcement with a larger pedicled temporal muscle and fascia flap on the outer surface to improve success. The bone defect is then filled with a mixture of medical adhesive, bone chips, or muscle fragments. If the skull defect communicates with a paranasal sinus, the sinus mucosa is curetted, the sinus cavity is packed with muscle, and the bone defect is sealed. The wound is closed in layers without drainage. Postoperatively, intracranial pressure should be reduced, and aggressive antibiotic therapy is administered. Common medical adhesives include isobutyl-2-cyanoacrylate (IBC), methyl cyanoacrylate, and alkyl-2-cyanoacrylate (Biobond, Aron-Alpha).

2. Cerebrospinal fluid otorrhea repair surgery: The specific location of the otorrhea must be identified preoperatively. If the otorrhea is caused by a middle cranial fossa fracture involving the tegmen tympani, allowing cerebrospinal fluid to directly enter the middle ear cavity and flow into the external auditory canal through a ruptured tympanic membrane, it is classified as extralabyrinthine otorrhea. If the otorrhea is due to a posterior cranial fossa fracture involving the labyrinth, creating communication between the subarachnoid space and the middle ear cavity, it is classified as intralabyrinthine otorrhea. The surgical approaches for these two types differ. For middle cranial fossa otorrhea, a temporal-occipital bone flap craniotomy can be used for repair. A curved temporal skin flap centered around the external auditory canal and mastoid is created, with the bone flap base positioned as close as possible to the middle fossa. Initially, the tegmen tympani area is explored extradurally along the anterior surface of the petrous bone to identify any fistula openings. If no fistula is found, the exploration should proceed intradurally. Care must be taken to avoid excessive medial dissection in the middle fossa to prevent injury to the greater superficial petrosal nerve, trigeminal nerve, middle meningeal artery, and cavernous sinus. Once the fistula opening is identified, the sealing and repair methods are as described above. If the fracture involves the posterior surface of the petrous bone, this approach can also address the posterior fossa. The tentorium is incised along the posterior edge of the petrous ridge, taking care to avoid injury to the superior petrosal sinus and sigmoid sinus. Reflecting the tentorium allows exploration of the fistula opening on the posterior petrous surface, which is typically located slightly lateral to the internal auditory canal. The area often shows cerebellar tissue and arachnoid membrane protrusion, making it easier to identify. Fistula openings in this region are difficult to suture and are usually sealed with muscle or fascial grafts coated with medical adhesive, followed by coverage with a pedicled muscle flap for fixation. After surgery, the scalp layers are meticulously sutured without drainage. Postoperatively, intracranial pressure should be reduced, and aggressive antibiotic therapy is essential. Alternatively, for intralabyrinthine otorrhea, the fistula opening on the posterior petrous surface can also be repaired via a suboccipital cranial approach.

3. Cerebrospinal fluid wound fistula (cutaneous fistula disease): First, non-surgical treatment should be carefully implemented, with vigorous efforts to control infection. At the same time, a ventricular puncture should be performed on intact scalp areas more than 6 cm away from the fistula, or a contralateral ventricular puncture for continuous drainage, or a lumbar puncture with catheter placement for cerebrospinal fluid drainage. The drainage volume should be adjusted until the fistula stops leaking fluid, avoiding excessive drainage. If there is no acute inflammation at the fistula site, the necrotic edges of the skin can be trimmed, followed by full-thickness suturing. If acute inflammation is present, pus and necrotic tissue should be cleared, the area cleaned and disinfected, and dressings changed regularly to promote healthy granulation tissue growth. Once acute inflammation is under control, delayed suturing or skin grafting over the granulation tissue can be performed to close the wound and seal the fistula.