3.1. Symptoms and presentation
SIH is an uncommon cause of headache and may present in association with a wide constellation of neurological symptoms. Postural headache is common but certainly not universal. Retrospective analyses have demonstrated diplopia to be the strongest positive predictor of CSF leaks in suspected SIH. Less commonly reported are presentations without any headache, as well as trigeminal neuralgia, syringomyelia, and acute cervical radiculopathies.
Unmanaged SIH may have unfavorable outcome including bilateral subdural hematomas and inferior displacement of posterior fossa elements. Thus, physicians treating suspected SIH must remain vigilant for development of potentially lethal complications, particularly in the elderly or those on anticoagulation who are more at risk for intracranial hemorrhage.
3.2. Diagnosis and evaluation
Diagnosis of SIH is made on the basis of symptoms, history, and MR findings. Although lumbar puncture is generally unnecessary, a CSF opening pressure of less than 60 cm of water is a classic finding. MR findings of pachymeningeal enhancement, venous engorgement, pseudo-subarachnoid hemorrhage, pituitary hyperemia, and/or cerebellar tonsil “sagging” (A) are helpful diagnostic features. Spinal imaging is generally reserved for patients with SIH who do not respond to non-directed EBP. Precise localization of the leak is best accomplished with CT myelography, though there is increasing interest in gadolinium myelography. In our case, high resolution CT myelography not only confirmed CSF extravasation but also identified the causative osteophyte for the dural defect.
3.3. Non-surgical therapy
Bed rest and hydration, intravenous caffeine and theophylline, as well as steroid therapy, have all provided temporary relief as part of conservative treatment regimens. EBP, which can provide symptomatic relief in as short as 2 h, often serve as first line therapy for CSF leaks of spontaneous or iatrogenic etiology. In the setting of failed patch attempt, reducing CSF pressures with acetozolomide and the use of reverse Trendelenburg position has been shown to enhance success.
In refractory leaks, efforts should be made towards specific localization of the leak followed by directed therapy, such as CT-guided percutaneous epidural injection of fibrin sealant, which is especially useful for excellent localization of large meningeal diverticula or tears.
3.4. Neurosurgical management
The surgical algorithm involves ligation or repair of overt diverticula and tears, or packing of the epidural space with a hemostatic agent when the source of the leak is not apparent. Dural injury by spinal osteophytes or disc herniation is rarely reported. Surgical treatment of CSF leaks caused by spinal osteophytes includes removal of the offending bone spur with surgical tamponade of the dural tear. Anterior approaches, as well as non-invasive EBP, have been reported. In our patient, a posterior approach was chosen to decrease morbidity.
In general, the posterior approach is indicated in patients with acute comorbid pathologies such as widespread malignancy, spinal cord compression, or poor tolerance to the anterior approach. However, in patients with pathology confined to anterior elements and who do not require posterior instrumentation, such as ours, there is no clear contraindication to anterior access. The benefits of anterior exposure, namely excellent visualization, have to be balanced against the risk of greater soft tissue damage and extended length of the operation. In our case, given the patient's low-normal BMI, youthful boney elements, and localized target, we were confident adequate exposure could be obtained via the posterior approach. In addition, the posterior angle allowed for the tacking of the dural repair to tamponade the source of the CSF leak since primary closure was not possible.
Furthermore, acute neurological decompensation secondary to expanding subdural hematoma requires immediate surgical intervention. In our patient, although evacuation was initially successful, the hematomas recurred on a smaller scale. Continuous intrathecal saline infusion via lumbar drain has been used to directly augment intracranial pressure by replacing lost fluid, and has been reported in the setting of severe SIH to aid in restoring physiology CSF volume and flow.