Abstract
Dr Brazis has written a review of the literature on the clinical manifestations of idiopathic intracranial hypertension, possible associated venous hypertension and intracranial dural venous sinus abnormalities, and a brief discussion of medical and surgical therapies. The preferred terminology for this condition is idiopathic intracranial hypertension, but pseudotumour cerebri is so engrained in the literature that it stubbornly remains (1). The manuscript covers the literature well, and the information reviewed serves as an excellent reference source for interested readers. Unfortunately, Dr Brazis has noted the conflicting expert opinions regarding success, failure and complications for each of the surgical procedures, and, as a result, his summary discussion is barren of any algorithm of management, or even recommendations in approaching these difficult patients.
Dr Brazis has written a review of the literature on the clinical manifestations of idiopathic intracranial hypertension, possible associated venous hypertension and intracranial dural venous sinus abnormalities, and a brief discussion of medical and surgical therapies. The preferred terminology for this condition is idiopathic intracranial hypertension, but pseudotumour cerebri is so engrained in the literature that it stubbornly remains (1). The manuscript covers the literature well, and the information reviewed serves as an excellent reference source for interested readers. Unfortunately, Dr Brazis has noted the conflicting expert opinions regarding success, failure and complications for each of the surgical procedures, and, as a result, his summary discussion is barren of any algorithm of management, or even recommendations in approaching these difficult patients.
It is helpful to separate significant and progressive neurological visual loss from the symptoms of headache in this condition, because significant and progressive visual loss is an absolute indication for aggressive surgical cerebrospinal fluid (CSF) diversion and lowering of intracranial pressure (ICP), whereas headache, although of concern to the patient, is not. Most neurosurgeons and ophthalmological surgeons, in concert with neurologists, particularly headache neurology specialists and interventional neuroradiologists, work as a team in the consensus management of these patients, so communication between these specialists is concentrated on the best strategy for managing each individual patient.
As a clinician familiar with this disorder for > 20 years, I submit that obesity plays a major role in the aetiology for most patients, and may play a role in the increasing prevalence of the disorder (2). Although I know of no study documenting routine lumbar puncture and ICP measurement in obese patients, my experience suggests that ICP in obese patients is probably higher than in patients with normal body habitus. The threshold for ICP to cross into the hypertensive realm affects a small but significant percentage of these patients, perhaps due to a myriad of contributory factors, including impaired venous and/or CSF egress, impaired autoregulation, and associated systemic factors of vascular hypertension, sleep apnoea, or chronic CO2 retention. Regardless, pernicious elevation of ICP ensues, with the symptoms and signs nicely summarized by Dr Brazis.
Clinicians faced with patients suspected of harbouring idiopathic pseudotumour cerebri do well to remember that it is a diagnosis of exclusion. This means that high-quality ≥ 1.5-T magnetic resonance imaging (MRI), with MR angiography (MRA) and venography (MRV), are mandatory to rule out mass lesions, dural venous sinus thrombotic occlusion, and venous hypertension induced from dural arteriovenous fistula, and parenchymal fistula or arteriovenous malformations. If necessary, diagnostic catheter angiography may be required to rule out a vascular malformation in the brain parenchyma, dura or surrounding skull base region. Despite the discussion in this manuscript of venous sinus stenosis, ectasia, etc., as abnormalities associated with idiopathic pseudotumour cerebri, a thrombosed major intracranial venous sinus, particularly the superior sagittal sinus, is not pseudotumour cerebri, and is managed quite differently as a result. As a consequence, MRI and MRA/MRV must rule out lesions detrimental to the patient's health that produce symptoms and signs of elevated increased ICP, documented by a lumbar puncture revealing elevated ICP in a relaxed recumbent position, followed or preceded at any point by ophthalmological assessment of the optic nerve head with photography, and visual field testing as dictated by the findings. The majority of these patients will be obese, perhaps severely so, and in my view this is a major early treatment consideration in this condition, both in managing the elevation in ICP and in reducing the morbidity and mortality associated with obesity.
Designing an algorithm for managing these patients is difficult, and obviously patient selective. The team of physicians involved in managing this disorder are encouraged to communicate freely, but are generally anchored by the neurologist, who serves as the focal point for the patient and their family. As mentioned above, documented progressive visual loss necessitating aggressive medical and surgical management should be separated from the symptoms of headache in any algorithm. Many of these patients will have functional overlay, depression, and emotional issues compounding their somatic complaints. Surgical CSF diversion is clearly indicated in patients with documented visual loss. However, the complications may occasionally be serious, and have been concisely reviewed by Dr Brazis in this manuscript. Although potentially incapacitating, no one suffers neurological deficit from headaches alone. The risk of death from ventricular or lumbar peritoneal shunting and permanent visual loss induced from optic nerve sheath fenestration is all low risk, but these are very real complications (2, 3). Therefore, for headache alone, a strategy should be in place to select patients before committing to surgical CSF diversion procedures with known neurological complications, and low but real risks of death or neurological injury.
Managing headache alone
I submit that managing headache alone should follow some provocative testing to associate the headache more clearly with CSF dynamics. This would be in the form of serial lumbar punctures, or serial CSF withdrawal from exteriorized lumbar drains. In a related context, the question of normal pressure hydrocephalus can be similarly assessed as to potential for shunt response by CSF withdrawal, and follow-up neurological evaluation. It is a cogent argument that in patients with incapacitating headache and suspected or overt psychological overlay, who have failed medical therapy, CSF withdrawal by serial lumbar punctures or exteriorized lumbar drains may be an invaluable test to assess headache response. If conducted as both a sham and actual CSF withdrawal, these provocative tests, along with clinical acumen, will help select patients as ideal candidates for surgical CSF diversion procedures for their headache alone.
Documented visual loss
If we isolate visual loss alone in an algorithm, then clinically I believe the management is neurologically directed to prevent, stabilize or reverse visual loss, the most severe sequelae of uncontrolled elevated ICP in this syndrome. The following algorithm follows a common sense approach. If visual loss is documented as mild or enlarged blind spots alone, then the medical arm may be followed initially. However, progressive or significant visual loss should proceed directly to more aggressive therapies. Although by no means applicable to all patients, and clinicians may disagree, the following may serve as a treatment strategy for the neurological management of this condition:
Some pearls to consider in managing these patients:
Significant weight loss alone may reverse the condition, as well as the associated medical comorbidities of hypertension and sleep apnoea. Weight loss also lowers ventricular peritoneal shunt failures, which more commonly occur at the peritoneal catheter, due in part to the increased abdominal pressure in obese patients (4). Aggressive management of obesity cannot be overemphasized, and should be initiated as early as possible. Weight loss with gastric bypass is faster than with gastric banding overall, but, in general, the end result is very similar. As a consequence, a discussion with a bariatric surgeon as to the goals of this surgery, in correlation with the malignancy of the intracranial hypertension, should be a consideration in markedly obese patients early in their management.
Serial lumbar puncture, or lumbar drain placement, can be useful medical strategies. Repetitive lumbar puncture with the needle bevelled perpendicularly to the dural tube, may produce a pin cushion effect—creating a CSF diversion to the surrounding epidural fat, which in a small subset of patients may be all that is necessary (in combination with weight loss). Placement of a lumbar drain for a day or two can produce the same effect, as a moderate sized sylastic drain creates a larger opening that may remain patent when removed, providing continued CSF egress under high pressure to the surrounding fat (similar to optic nerve sheath fenestration). In fact, an occasional patient will need a stitch in the skin to keep the CSF contained, as it often dissects its way under pressure to the skin surface after a drain has been removed.
All of the surgical procedures listed in the algorithm, and thoroughly discussed by Dr Brazis, have advantages and disadvantages. I have a preference for recommending stereotactically placed ventricular peritoneal shunts as perhaps the first line of surgical therapy, although clearly successful results may be mirrored with any of these procedures. However, both ventriculo-peritoneal and lumbo-peritoneal shunts will have increased failures at the peritoneal end unless significant weight loss is part of the treatment regimen. For abdominal access, it is often useful to avoid midline abdominal incisions and utilize a subcostal approach, and to have a general surgeon direct the catheter to the paracolic gutters of the abdomen. This will increase the success rate of catheter drainage in markedly obese patients, and prevent loculation of the fluid in the intestinal folds or omental fat regions. It can also be argued to remove any slit valves from the distal abdominal catheter, as these have increased frequency of causing shunt failure by sequestering omental fat within the lumen of the tube (5).
SUMMARY
These patients are difficult and require expertise in multiple areas of management, especially if progressive visual loss is documented. A headache neurologist familiar with this disorder serves as the anchor for the rest of the team, and is essential in directing strategies of care. Headache alone and visual loss with or without headache should be treated separately in managing this condition.