**Abstract**

Encephaloceles and cereberospinal fluid (CSF) leaks of the ventral skull base resulting from trauma (surgical and non-surgical), neoplasm, congenital, and spontaneous are a complex problem typically managed by rhinologists/skull base surgeons. Conservative management is often the first step in managing these complex problems. Endoscopic repair of CSF leaks and encephaloceles has greatly evolved with the evolution of endoscopic visualization and instrumentation. Endoscopic repairs of CSF leaks are effective and offer decreased morbidity compared to open approaches with comparative success rates. Meticulous technique is key to success in repair of skull base defects. Materials used are often less important than quality of repair.

**Keywords:** CSF leaks, Encephaloceles

## **1. Introduction**

Cerebrospinal fluid (CSF) is produced by the choroid plexus in the lateral ventricles, third, and fourth ventricles at a rate of 0.35 mL/min (20 mL/hour or 350–500 mL/day) in the normal physiologic states and is reabsorbed into the dural venous sinuses through the arachnoid villi. The total volume of circulating CSF is 90–150 mL. The entire volume of CSF turns over three to five times per day. Typical intracranial pressure is 5–15 cm H2O and is considered elevated when it is greater than 15 cm H2O. The three layers of the meninges are the dura mater, arachnoid, and pia mater. The dura mater is separated into the superficial layer and the meningeal layers. Common causes of CSF leaks can be divided into trauma, both surgical and nonsurgical, neoplasm, congenital, and spontaneous [1].

An encephalocele is herniation of neural tissue through a defect in the skull base and is defined by the type of tissue that herniates through the defect. A meningocele contains herniated meninges, a meningoencephalocele contains herniated brain matter and meninges, and a meningoencephalocystocele is made up of herniated brain matter and meninges that communicate with a cerebral ventricle.

## **2. Etiology**

#### **2.1 Cerebrospinal fluid leak**

The most common cause is nonsurgical (70–80%). 1–3% of acute head injuries result in a CSF leak. Conservative management is often the first step in managing CSF leaks resulting from acute trauma. Seventy percent of leaks close spontaneously with observation and conservative management which may include bed rest, head of bed elevation, and lumbar drainage. Overall, there is a 30–40% risk of meningitis with conservative treatment [2].

Surgical causes (planned and unplanned) make up a large portion of leaks requiring intervention. Functional endoscopic sinus surgery (FESS) carries <1% incidence of CSF leak. The most common site of skull base injury is the lateral lamella of the cribriform plate. The posterior ethmoid skull base is at greater risk when the maxillary sinus is highly pneumatized in the superior–inferior dimension, which creates a relatively decreased posterior ethmoid height. Neurologic Surgery caries an increased risk albeit typically include planned CSF leak with expected violation of the meninges. Transsphenoidal approach for sellar and suprasellar lesions carry a reported 0.5–15% incidence of CSF leak [3].

Neoplasms can result in CSF leak via direct tumor invasion and/or mass effect leading to intracranial hypertension. Congenital causes result from failure of closure of developmental spaces with resultant herniation of intracranial contents. Foramen cecum is the most common location. Spontaneous leaks are often the result of idiopathic intracranial hypertension (IIH) resulting from decreased CSF reabsorption. Patient characteristics and symptoms often include middle-age, obesity, female, pressure-type headaches, pulsatile tinnitus, and balance dysfunction.

Empty sella syndrome is a radiographic appearance of CSF-filled sella due to flattening of the pituitary gland which is an endocrine gland that resides in the sella turcica and functions to control other endocrine glands by secretion of controlling hormones. Empty sella syndrome can be seen in IIH, which typically affects obese women. Patients typically will present with headaches, pulsatile tinnitus, and diplopia. A hallmark physical exam finding is bilateral optic disc edema secondary to increased intracranial pressure (ICP). Treatment is focused on decreasing ICP with pharmacologic therapy consisting of acetazolamide and furosemide to lower ICP, and headache management, which may include amitriptyline and propranolol. In severe cases with vision problems, surgical intervention may be required, including optic nerve decompression or CSF shunting. Empty sella syndrome can be seen in conjunction with spontaneous CSF leaks.

#### **2.2 Encephalocele**

Encephaloceles can occur in both the skull and spinal column. Twenty percent occur within the cranium and 15% of these are associated with the nasal cavity. Nasal encephaloceles are divided into two types: sincipital and basal. Sincipital (anterior and superior) encephaloceles make up approximately 60% of nasal encephaloceles and typically present as a soft compressible mass over the glabella. Basal encephaloceles occur through the skull base more posteriorly and make up approximately 40% of nasal encephaloceles. They may remain hidden for many years because they are located more posteriorly than the sincipital type.

## **3. Clinical presentation**

Clear rhinorrhea that is unilateral, watery, and salty to taste is the most common complaint in CSF leaks. It may run out of the nose in more anterior leaks, or down the back of the throat in more posterior leaks. The drainage can be exacerbated by the Dandy maneuver, which entails tilting the head forward into a chin-tuck position and straining.

Patients with an encephalocele will often present with rhinorrhea or recurrent meningitis and may have a broad nasal dorsum or hypertelorism. Encephaloceles may

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*Cerebrospinal Fluid Leaks and Encephaloceles DOI: http://dx.doi.org/10.5772/intechopen.91374*

**4. Investigations**

**5. Management**

**6. Surgical Intervention**

than the quality of the repair [6].

characteristically transilluminate, expand with the Valsalva maneuver, and demonstrate a positive Furstenberg sign (enlargement with compression of internal jugular veins). Radiologic imaging including computed tomography (CT) and magnetic resonance imaging (MRI) may be used to evaluate the size and location of encephaloceles.

The most sensitive and specific test is qualitative β2-transferrin evaluation of the nasal drainage. β2-transferrin is detected in few fluids in the body including CSF, perilymph, and aqueous humor. Only 0.2 mL is needed for an adequate specimen. β2-transferrin has a sensitivity of 97% and specificity of 93%. False positive results can occur with abnormal transferrin metabolism from chronic liver disease, glycogen metabolic disease, and carcinomas; therefore, results should be verified with a negative serum β2-transferrin. β-trace protein is a newer laboratory test with higher

The radiologic evaluation of a CSF leak can be extensive and often begins with a fine cut maxillofacial CT scan to demonstrate bony abnormalities such as defects and fractures. CT is the mainstay for radiologic workup of CSF rhinorrhea with a sensitivity of 92% and a specificity of 92–96%. If the initial imaging does not show an obvious abnormality but suspicion is still high, a CT cisternogram may be useful. This study entails injection of radiopaque material through a lumbar drain into the intrathecal space to help delineate the CSF leak. Presence of contrast within the nasal space or paranasal sinuses indicates a CSF leak. CT cisternography has a sensitivity of 92% with an active leak to 40% with an intermittent leak. MRI cisternography (T2 weighted fast-spin protocol) can be helpful in cases of neoplasm, meningoencephalocele, encephalocele, and in patients with an iodine allergy.

In patients who have a traumatic leak and normal CSF pressure, conservative treatment consists of bed rest with head of bed elevation and lumbar drainage of CSF for 5–10 days. With conservative management, there is a reported risk ranging from 7 to 30% of ascending meningitis. The incidence of spontaneous resolution

The general consensus among practicing otolaryngologist is that antibiotics should not be used for conservative management unless there is a very large defect with comminuted bone of the skull base as a simple CSF leak carries a 7% infection rate (meningitis, intracranial abscess, cellulitis abscess, and osteomyelitis) and prophylactic antibiotics have not been shown to decrease the risk of infection. After endoscopic repair, antibiotics are generally recommended for 24–48 hours including Cefazolin (1 gm q8), Vancomycin (1 gm q12), or Clindamycin (600 mg q8). This is done to cover possible contamination at the time of surgery in a non-sterile field with concomitant sealing of the sterile to non-sterile flushing of an active leak [4, 5].

Endoscopic repair of CSF leaks is effective and offers decreased morbidity compared to open approaches. Meticulous technique is key to success in repair of skull base defects. Materials used and procedures employed are less important

with conservative management is reported to be 70%.

sensitivity and specificity which offers faster results than β2-transferrin.

characteristically transilluminate, expand with the Valsalva maneuver, and demonstrate a positive Furstenberg sign (enlargement with compression of internal jugular veins). Radiologic imaging including computed tomography (CT) and magnetic resonance imaging (MRI) may be used to evaluate the size and location of encephaloceles.
