29 Cerebrospinal Fluid Leaks & Encephaloceles Flashcards
What are the most common causes of CSF leaks?
What are the most common causes of CSF leaks?
- Trauma
- Nonsurgical: Most common etiology (70% to 80%). One percent to 3% of acute head injuries result in a CSF leak. 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% to 40% risk of meningitis with conservative treatment.
- Surgical (planned and unplanned):
- FESS (<1% incidence of CSF leak): 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 (Figure 29-1).
- Neurologic Surgery: Transsphenoidal approach for sellar and suprasellar lesions (0.5% to 15% incidence of CSF leak)
- Neoplasm: Mechanisms include direct tumor invasion and/or mass effect leading to intracranial hypertension.
- Congenital: Failure of closure of developmental spaces with resultant herniation of intracranial contents. Foramen cecum is the most common location (50%).
- Spontaneous: 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.
Figure text:
A relatively short height of the ethmoid sinus (top arrow) as a result of a highly pneumatized, tall maxillary sinus (bottom arrow).
What is empty sella syndrome and how is it treated?
What is empty sella syndrome and how is it treated?
Empty sella syndrome is a radiographic appearance of CSF-filled sella due to flattening of the pituitary gland (Figure 29-2). The pituitary gland is an endocrine gland that resides in the sella turcica and functions to control other endocrine glands (adrenal glands, thyroid, ovaries, testicles) 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.
What is an encephalocele?
What is an encephalocele?
An encephalocele is herniation of neural tissue through a defect in the skull base (Figures 29-3 and 29-4) and is defined by the type of tissue that herniates through the defect. A meningocele contains herniated meninges, a menigoencephalocele contains herniated brain matter and meninges, and a meningoencephalocystocele is made up of herniated brain matter and meninges that communicate with a cerebral ventricle.
Where do encephaloceles occur?
Where do encephaloceles occur?
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.
How is an encephalocele diagnosed?
How is an encephalocele diagnosed?
Patients will often present with rhinorrhea or recurrent meningitis and may have a broad nasal dorsum or hypertelorism. Encephaloceles may 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 (see Figures 29-3 and 29-4).
Describe the physiology of CSF production.
Describe the physiology of CSF production.
CSF is produced by the choroid plexus of the lateral, third and fourth ventricles at a rate of 0.35 mL/min (20 mL/hr or 350 to 500 mL/d) in the normal physiologic states. The total volume of circulating CSF is 90 to 150 mL. The entire volume of CSF turns over three to five times per day. Typical intracranial pressure is 5 to 15 cm H2O and is considered elevated when it is greater than 15 cm H2O.
What is the most common complaint in patients presenting with concern for a CSF leak?
What is the most common complaint in patients presenting with concern for a CSF leak?
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.
What laboratory tests can be performed to diagnose a CSF leak?
What laboratory tests can be performed to diagnose a CSF leak?
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 sensitivity and specificity which offers faster results than β2-transferrin, however it is not universally available.
Describe the radiologic evaluation of a patient with CSF rhinorrhea.
Describe the radiologic evaluation of a patient with CSF rhinorrhea.
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% to 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.
Describe the workup of suspected CSF rhinorrhea.
Describe the workup of suspected CSF rhinorrhea.
- If β2-transferrin or β-trace protein is positive, obtain a fine cut maxillofacial CT scan to assess for source.
- If β2-transferrin or β-trace protein is negative, and clinical suspicion is low, workup is complete. If clinical suspicion remains high, evaluate with maxillofacial CT.
- If a single, small (less than 1 cm) bony defect is present on the CT in a patient with normal intracranial pressure, conservative therapy may be attempted. If the bony defect is greater than 1 cm, or if the patient has elevated intracranial pressure and a high-pressure leak, surgical management is recommended.
- If more than one bony defect is seen on CT imaging, cisternography can be helpful in determining which site(s) is/are leaking.
- If no bony defect is detected on maxillofacial CT, repeat β2-transferrin or β-trace protein may be sent. If positive, CT or MRI cisternogram is recommended. If negative, and clinical suspicion is high, surgical exploration is indicated, possibly with utilization of intrathecal fluorescein.
- If a bony defect is present on CT with associated soft tissue mass, MRI or MRI cisternogram is recommended to further evaluate the characteristic of the soft tissue mass, which may represent a meningocele or other neoplasm.
What does conservative therapy for CSF leaks entail?
What does conservative therapy for CSF leaks entail?
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 to 10 days. With conservative management, there is a reported risk ranging from 7% to 30% of ascending meningitis. The incidence of spontaneous resolution with conservative management is reported to be 70%.
Should antibiotics be used in patients with known CSF rhinorrhea?
Should antibiotics be used in patients with known CSF rhinorrhea?
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 (1gm q8), Vancomycin (1gm q12), or Clindamycin (600mg 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.
How has surgical management of CSF leaks improved with the use of endoscopic surgery?
How has surgical management of CSF leaks improved with the use of endoscopic surgery?
Advancements in the endoscopic surgical repair of CSF leaks and encephaloceles have resulted from improvements in instrumentation, visualization, access, and technique. Improved diagnostic imaging and surgical navigation have also improved management. Advancements in endoscopic reconstructive techniques of the skull base including utilization of local vascularized flaps have improved success rates with endoscopic approaches.
Describe the use of intrathecal fluorescein in the surgical repair of CSF leaks.
Describe the use of intrathecal fluorescein in the surgical repair of CSF leaks.
Its advantages include the ability to stain defects that may be more difficult to identify clinically, through the visible dye of CSF to a light green color. The surgeon can also use it to confirm a water-tight repair. It carries a 0% false positive rate. Its disadvantages include a moderate false negative result. It requires a lumbar puncture, and the use of fluorescein intrathecally is not FDA-approved. Rare complications including seizures (0.3%) and death have been reported; however, these have more commonly been associated with administration through a suboccipital puncture. If used to help localize a CSF leak it should be used with caution and should be dosed as 0.05 to 0.1 mL per 10 kg body weight up to maximum 0.1 mL 10% fluorescein. This is mixed in 10 mL of preservative-free normal saline or CSF. The surgeon should inject slowly (over 5 to 10 min) without paralytics in the anesthetic regimen to assess for seizure activity. Fluorescein should be avoided in patients with abnormal renal function.
What are the goals of skull base reconstruction?
What are the goals of skull base reconstruction?
The primary goal in endoscopic repair of CSF leaks and skull base reconstruction is to definitively identify all leaks in order to completely reconstruct all defects. After identifying the leak or leaks, the goals of reconstruction are creation of a safe barrier with separation of intracranial and sinonasal spaces and elimination of any dead space. As with any surgical intervention, meticulous surgical technique is paramount for success.
