Headache, Cerebrospinal Fluid Leaks, and Pseudomeningoceles after Resection of Vestibular Schwannomas: Efficacy of Venous Sinus Stenting Suggests Cranial Venous Outflow Compromise as a Unifying Pathophysiological Mechanism

Abstract

Background  Regardless of the operative approach, headache, cerebrospinal fluid (CSF) leaks, and pseudomeningoceles remain disproportionately common problems after surgery for vestibular schwannomas and have a significant negative impact on quality of life and potential to return to full employment. Recent work has raised the possibility that these problems may, in part, be related to acquired obstruction of cranial venous outflow. This article explores this idea further with respect to a group of patients with severe and intractable symptoms.

Objective  The main objective of this article is to describe our experience diagnosing, investigating, and treating cranial venous outflow obstruction following translabyrinthine resection of vestibular schwannomas.

Methods  Retrospective review of all patients ( n  = 9) at our institution referred for sigmoid sinus stenting following translabyrinthine surgery.

Results  Headache resolved or improved after sigmoid stenting in all five patients in whom it was the primary symptom. CSF leak was the primary problem in two patients. In one, the leak was unchanged, but headache improved. In the other, the leak resolved, and headache improved. Two patients had symptomatic pseudomeningoceles and both resolved

Conclusion  Assuming a meticulous approach to wound closure, a CSF leak following surgery for vestibular schwannoma can be viewed as a pathological, but essentially homeostatic, response to raised intracranial pressure caused by acquired obstruction to cranial venous outflow. Postoperative headache (from high or low intracranial pressure) and CSF leaks, therefore, may all respond to measures aimed at eliminating the obstructing lesion.

Introduction

Although headache may precede surgery for vestibular schwannomas, sometimes it develops de novo in the early or late postoperative period and can be severe, debilitating, and persistent. ^{1 2 3 4}

Cerebrospinal fluid (CSF) leaks and pseudomeningoceles imply an acquired defect in the dura which allows escape of CSF either into the middle ear or subcutaneous tissues; in the case of a CSF leak, relatively unhindered by any physical barrier, in the case of a pseudomeningocele, contained in a collection by intact skin and subcutaneous tissue. Either can be very difficult to manage.

The incidence of these complications is widely recognized to be disproportionate to that after supratentorial craniotomy. ^{5 6 7 8 9 10} So, what makes these patients so susceptible to them? No universally accepted explanation has been forthcoming regarding headache, except for those secondary to a CSF leak. ⁶ Regarding CSF leaks and pseudomeningoceles, communicating hydrocephalus has been observed in relation to vestibular schwannomas at presentation, associated with elevated CSF protein levels, and it has been proposed that this reflects accumulation of tumor debris in the CSF, which interferes with CSF absorption. ^{11 12 13} One could speculate further that a similar mechanism might apply in patients who show no hydrocephalus preoperatively, the underlying problem eventually declaring itself as delayed healing of an iatrogenic dural defect. ¹⁴

We have seen narrowing of the sigmoid sinus where it crosses the craniectomy defect following vestibular schwannoma surgery and published a report in which repair of this narrowing by stenting brought about resolution of postoperative headache. ¹⁵ Similarly, we have published a report in which jugular venous narrowing was responsible for a spontaneous CSF leak which resolved after stenting. ¹⁶ Could postoperative venous sinus narrowing, therefore, provide a unifying pathophysiological mechanism for these complications following translabyrinthine surgery?

Venous sinus stenting is rapidly gaining acceptance as a safe and reliable alternative to CSF diversion procedures in certain instances of raised intracranial pressure ¹⁷ and in this article we describe the results of venous sinus stenting in nine patients who became newly symptomatic following translabyrinthine surgery. We discuss the implications for etiology and management.

Patients and Methods

Patients

The case notes of all patients referred for sigmoid sinus stenting following translabyrinthine surgery for vestibular schwannoma were reviewed by two of the authors (Higgins and Macfarlane) ( Figs. 1 – 3 ). There were nine patients altogether, all referred at the discretion of the treating physician, six male and three female, average age = 47 years (range, 29–59). In five patients, the primary symptom was headache, in two a CSF leak, and in two there were pseudomeningoceles which threatened the viability of an auditory brain stem implant. Most patients also had other symptoms, for example, fatigue, dizziness, imbalance, visual disturbance, and memory dysfunction ( Table 1 ).

Fig. 1.

Patient 1 with headache: ( A ) Axial magnetic resonance imaging shows the fat graft (arrow) at the site of surgery to protect against cerebrospinal fluid leakage. ( B ) Axial computed tomography (CT) shows thinning of the sigmoid sinus (arrows) as it crosses the surgical defect. ( C ) Frontal subtracted view catheter venogram: catheter tip (block arrow) at the torcula opacifies blood draining through the transverse and sigmoid sinuses on both sides to the jugular veins (JV). Left sigmoid sinus narrowing (arrows) is poorly delineated with this technique in this case. However, a similar view post stenting ( D ) shows expansion of the sigmoid sinus at the site of the stent (arrows). ( E ) Axial CT follow-up shows the inferior end of the stent (arrows) as it turns into the jugular foramen. (Apparent waisting of the stent reflects “out of plane” curvature of the sigmoid sinus at this level.)

Fig. 3.

Patient 4 with headache, sigmoid, and jugular narrowings. Axial computed tomography images show ( A ) narrowing of the sigmoid sinus where it crosses the craniectomy defect (arrows) and ( B ) narrowing of the right jugular vein (thin arrow) between the styloid process (block arrow) and lateral mass of the C1 vertebra (asterisk). ( C ) The styloid process has been resected to allow space for a stent. ( D ) and ( E ) show the sigmoid (arrow) and jugular (arrow) stents in situ.

Table 1. Patients referred for ipsilateral sigmoid sinus stenting after translabyrinthine resection of vestibular schwannoma.

Patient	Age	Sex	Primary symptom after surgery	Other symptoms	Other interventions between tumor resection and sigmoid stenting	Interval between tumor resection and stenting (months)	Further procedures following sigmoid stenting	Outcome (and follow-up in months)
1	41	M	Headache	Flu-like aches in back and legs	None	22	None	Immediate near complete resolution of all symptoms with no recurrence to date (60 months)
2	50	M	Headache	Fatigue	None	33 (ipsilateral transverse sinus stented at same time)	In-stent angioplasty	Immediate near complete resolution of all symptoms after sigmoid stenting. Partial recurrence at 2 years. Immediate resolution of all symptoms after second procedure (42 months)
3	40	M	Headache	Otalgia, ataxia, imbalance	Titanium cranioplasty	29	Surgical enlargement of ipsilateral jugular foramen, angioplasty of sigmoid stents, stenting transverse sinus	Headache improved after initial sigmoid stenting, then recurred. Improved again by subsequent procedures (7 months)
4	29	M	Headache	Poor memory, imbalance, visual blurring	VP shunt; ipsilateral styloidectomy then jugular stent	92	None	Headaches improved following jugular stenting and improved further following sigmoid stenting (18 months)
5	62	F	Headache	Fuzzy head, dizziness, visual blurring	none	21	None	Fuzzy head, visual blurring resolved. Dizziness and headache improved (42 months)
6	59	M	CSF leak	Headache	Blind sac closure; later glue repair of wound	3	Repeat blind sac closure	Headache resolved immediately; leak unchanged. Second blind sac closure unsuccessful. Leak stopped after VP shunt (12 months)
7	54	M	CSF leak	Headache, meningitis	Lumbar drain, later clamped, then dislodged.	1	None	Headache improved. CSF leak resolved (8 months)
8	40	F	Pseudomeningocele	Blurred vision (mild headache); papilloedema	Lumbar puncture × 2	2	None	Pseudomeningocele gradually resolved; papilloedema gradually resolved (6 months)

Abbreviations: CSF, cerebrospinal fluid; VP shunt, ventriculoperitoneal shunt.

In the case of headache, sigmoid stenting was performed between 21 months and 7 years, 8 months after the onset of symptoms. In patient 3, sigmoid stenting was deferred until it was clear that repairing the craniectomy defect with cranioplasty had not improved headache. In patient 4, after failure of a ventriculoperitoneal shunt, an elective decision was made to treat ipsilateral internal jugular narrowing prior to stenting the sigmoid sinus.

In the case of CSF leaks, referral for sigmoid stenting followed shortly after the failure of a lumbar drain or blind sac closure with Eustachian tube obliteration. In the case of pseudomeningoceles, referral for stenting was made soon after translabyrinthine surgery as an alternative to lumbar drainage when the integrity of a brain stem implant was threatened by the subcutaneous swelling.

Diagnostics

CT Venography

All patients had computed tomographic (CT) venography demonstrating narrowing of the sigmoid sinus where it crossed the craniectomy defect ( Figs. 1B , 2B , 2B , 3A ). In all five patients with headache, this involved the nondominant side. In all patients with CSF leaks or pseudomeningoceles, the affected sinus was dominant.

Fig. 2.

Patient 8 with a pseudomeningocele: ( A ) Preoperative, T1 postcontrast magnetic resonance imaging shows bilateral vestibular schwannomas, much larger on the right. Axial ( B ) and coronal reformatted ( C ) computed tomography (CT) images following surgery show narrowing of the sigmoid sinus as it crosses the craniectomy defect (arrows) and the overlying pseudomeningocele (asterisk). There is an auditory brain stem implant in situ (block arrow); jugular veins (JV). ( D ) Frontal unsubtracted view catheter venogram immediately prior to stenting shows narrowing of the sigmoid sinus (arrows). Same unsubtracted view ( E ) shows the stent (arrows) and subtracted view ( F ) shows the expansion of the sinus (arrows). ( G ) Axial CT shows stent in situ (arrow), the brain stem implant undisturbed and resolution of the pseudomeningocele.

In two patients, the jugular bulb had been lowered at surgery but in neither case did CT show any appreciable narrowing of the venous conduit in this region as a result.

Lumbar Puncture

Four patients with headache had lumbar puncture as a diagnostic procedure. In three with opening pressures 18 to 23 cm H ₂ O, CSF drainage produced a temporary improvement or resolution of headache. In one with an opening pressure of 15cm H ₂ O, CSF drainage had no effect.

In other patients (with pseudomeningoceles or CSF leaks), lumbar puncture or lumbar drain insertion were performed only as therapeutic maneuvers.

Catheter Venography

Catheter cerebral venography establishes the pattern of cerebral venous outflow through the venous sinuses and jugular veins and allows measurement of intracranial venous pressures and detection of any focal pressure gradients along the venous outflow tracts. It is performed under local anesthesia, using a common femoral vein for access, a 4F catheter passed up into one of the internal jugular veins and a microcatheter (Rebar 27; Microvention) threaded through this catheter into the intracranial venous sinuses under X-ray guidance. Radiographic contrast media is injected through the microcatheter to look at flow and pressure measurements are recorded using a transducer connected at the catheter hub, referenced to zero at the mid axillary line.

All five patients with headache had catheter cerebral venography ( Fig. 1C , 2D ) in which pressures of 19 to 22 cm H ₂ O were recorded at the torcula with 4 to 7 cm H ₂ O pressure gradients between the torcula and right atrium, including 1 to 4 cm H ₂ O focal pressure gradients along the affected section of the sigmoid sinus. In patient 4, a 1 cm H ₂ O gradient along sigmoid sinus narrowing was compounded by a 2 cm H ₂ O gradient across narrowing of the jugular vein immediately downstream. In this instance, the jugular narrowing was treated first ( Fig. 3B and 3C ). In patient 3, a 2 cm H ₂ O gradient across the sigmoid narrowing was compounded by a 1 cm H ₂ O gradient across a congenitally narrow jugular foramen.

One patient (patient 8) with a pseudomeningocele ( Fig. 2 ) had catheter venography in which pressure at the torcula was recorded as 22 cm H ₂ O, and there was a gradient of 11 cm H ₂ O between the torcula and right atrium, which included 7 cm H ₂ O across the sigmoid narrowing. This patient also had papilloedema.

In one patient (patient 6) with a CSF leak venous pressures undertaken during sigmoid sinus stenting suggested additional narrowing of the ipsilateral jugular vein at the C1 level which was not addressed.

Interventions

Sigmoid Sinus Stenting

Sigmoid sinus stenting was performed under general anesthesia using a percutaneous jugular puncture. In this procedure, an 8F guide catheter, preceded by a 4F catheter, is advanced across the sigmoid defect under X-ray fluoroscopy before positioning a balloon mounted stent (Flexive; Boston Scientific) at the site of the defect, itself. The guide catheter is then withdrawn and the stent deployed by inflating the delivery balloon. Patients were anticoagulated with heparin during the procedure and treated with dual antiplatelets afterwards for 6 weeks, followed by a single antiplatelet for a further 6 weeks.

Styloidectomy and Jugular Stenting

In one patient (patient 4) with headache, narrowing of the jugular vein was judged important enough to likely interfere with the potential benefit of sigmoid sinus stenting. This patient had a jugular stenting procedure, after styloidectomy to allow safe deployment of the stent ( Fig. 3 ), an approach which has been described in a previous publication. ¹⁸

Transverse Sinus Stenting

In one patient (patient 2) with headache, the ipsilateral transverse sinus was narrow and was stented at the same time as the sigmoid sinus.

Jugular Foramen Enlargement

In one patient (patient 3) with headache treated by sigmoid stenting, transmastoid surgery to remove bone at the level of the jugular foramen was followed by further stenting to enlarge the ipsilateral venous conduit through the skull base.

Results

For Headache

Headache resolved or improved after sigmoid stenting in all five patients in whom it was the primary symptom, usually rapidly and, in two cases, immediately after the procedure. In one case (patient 2), published previously, ¹⁵ we now have further follow-up in that there was some regression at 2 years post stenting which was completely reversed by stretching up the stents with a balloon to fully match the size of the native venous conduit, initial stent sizing having been quite cautious. In another case (patient 3), further efforts to improve the size of the ipsilateral venous conduit by surgery and stenting through the jugular foramen and stenting of the transverse sinus produced incremental improvements in headache, although not resolution. In another case (patient 4), preliminary treatment of a jugular stenosis gave some symptomatic improvement and there was further improvement after sigmoid stenting.

For CSF Leaks

In one patient (patient 6), headache resolved immediately, but the CSF leak continued. In this patient, an ipsilateral jugular narrowing, associated with a 3cm H ₂ O pressure gradient, was noted at the C1 level at the time of stenting but not addressed. He had had a blind sac closure prior to stenting and had another afterwards, but the CSF leak did not resolve until insertion of a ventriculoperitoneal shunt.

In the other patient (patient 7), the CSF leak had already responded to lumbar drainage. However, after the drain was dislodged, concurrent anticoagulant therapy contraindicated replacement. Headache improved rapidly after sigmoid stenting and there was no recurrence of the leak.

For Pseudomeningoceles

One patient had two lumbar punctures which gave no benefit. In the other patient, multiple intrathecal spinal tumors precluded insertion of a lumbar drain. In both patients, the pseudomeningoceles gradually resolved after sigmoid stenting with no need for any further intervention.

Both of these patients also complained of blurred vision following tumor surgery. One patient, whose alternative cranial venous outflow was already compromised by sinus meningiomas (partially treated in a previous stenting procedure), had a recurrence of transient visual obscurations; these resolved after sigmoid sinus stenting. The other developed frank papilloedema: this and her visual symptoms also resolved after sigmoid stenting.

Discussion

The idea that iatrogenic venous sinus narrowing might be responsible for significant symptoms after translabyrinthine surgery has not been discussed in the medical literature. The cases we describe, however, which were all investigated with this possibility in mind, suggest not only that this is a viable proposition but also offer a mechanism wherein difficult and apparently disparate postoperative problems can be linked to a single structural cause.

This might seem implausible at first, but there is a precedent and model for connecting headache and CSF leaks (aside from headache caused by a CSF leak) in the medical condition known as idiopathic intracranial hypertension (IIH). This is a chronic and often disabling disorder of raised intracranial pressure, which can develop in either sex without any precipitating event. Headache and visual disturbance are the key symptoms. Importantly, there are no clinical signs, except those of raised intracranial pressure, of which papilloedema is the hallmark. ¹⁹

Pertinent to this discussion, IIH can present with a CSF leak, the assumption being that prolonged exposure of the dural membrane to elevated CSF pressure eventually causes it to give way at a weak point. This allows intracranial pressure to fall from its previously high value, often with amelioration of headache and resolution of papilloedema, although in some cases intracranial pressure falls to abnormally low values and new symptoms develop, including postural headache, which can completely eclipse any consideration of earlier intracranial hypertension. ^{20 21 22}

Headache from high intracranial pressure (which can have multiple phenotypes), spontaneous CSF leaks, and headache from low intracranial pressure, therefore, can all be symptoms of an underlying pathophysiological disturbance whose primary effect is to elevate intracranial pressure. ²²

IIH, itself, is defined by the absence of any identifiable cause, but cerebral venous sinus thrombosis is a known mimic, ²³ and in recent years, there has been debate regarding the role of cranial venous outflow obstruction in its etiology, short of venous sinus thrombosis. ²⁴ Most of this has centered around stenoses which have been observed at the transverse/sigmoid sinus junctions, and stenting has been proposed as a solution. ^{25 26}

So, is it possible that persistent headache, CSF leaks, and pseudomeningoceles after surgery for vestibular schwannoma are, for the most part, manifestations of the same underlying problem, essentially another mimic of IIH, caused by acquired obstruction to cranial venous outflow?

If they are, the cases we describe raise further questions about the effects of surgery on cerebral venous drainage, beyond that of damage to the ipsilateral sigmoid sinus. They also raise questions regarding the capacity of venous system to compensate for the loss of a venous conduit. Otitic hydrocephalus describes the acute syndrome of raised intracranial pressure following thrombosis of a dominant sigmoid sinus secondary to mastoiditis, and an awareness of the consequences of occluding dominant side venous drainage has long influenced the surgical approach to posterior fossa tumors. ²⁷ These cases, however, show that even compromise of a nondominant venous sinus can produce significant and long-lasting symptoms. Moreover, they raise the possibility that surgery may be damaging other parts of cranial venous outflow.

In patient 6, for example, ( Table 1 ) jugular venous narrowing at the C1 level ipsilateral to the side of sigmoid stenting was identified during the procedure but not addressed at the time and there was only partial resolution of symptoms: headache resolved but the CSF leak persisted. This may have been because not enough time was allowed for the dural defect to heal. Alternatively, jugular narrowing may have been a significant component of the physiological problem. In patient 4, this outcome was anticipated, and the jugular narrowing dealt with prior to sigmoid stenting.

In patient 3, the clinical course following sigmoid stenting, and subsequent procedures suggest that translabyrinthine surgery exposed a more widespread insufficiency of cranial venous outflow only partially resolved by treatment. ¹⁸

Regarding the jugular narrowings in this patient group, the obvious question is whether they were present before surgery or whether they are a consequence of the surgical procedure. This cannot be answered here but it is worth remarking that positioning for lateral skull base surgery often requires quite marked rotation of the head on the neck giving potential for compression and trauma to one or other of the jugular veins between the styloid process and the lateral mass of C1.

These postoperative problems, therefore, may be the product of several factors: local damage to the sigmoid sinus, injury to the jugular veins below the skull base, and poor compensatory reserve in the cerebral venous system, the latter dictated by individual venous anatomy.

Crucial to investigating these problems is an appreciation of the range and complexity of the symptoms that may accompany them. Aside from headache and CSF leakage, there may be fatigue, dizziness, myalgias, memory disturbance, anxiety, depression, and other complaints ( Table 1 ), ²¹ which can divert the clinician from considering the possibility of an organic disorder. Moreover, the problem is compounded by the usual absence of any clinical signs. Yet these symptoms are all seen in IIH, an unequivocally organic disorder, and not all patients with IIH have clinical signs. ^{28 29 30}

As it happens, the cases we describe all had intracranial pressures within accepted normal limits where papilloedema would not be expected anyway. However, this does not mean that their physiology is normal. Instead it lends weight to the idea that such symptoms can develop at much lower levels of intracranial pressure than generally recognized, regardless of whether there might be a CSF leak. This observation is critical. Moreover, it mirrors observations recorded in previous publications on tumor obstruction of the jugular foramen, ³¹ in relation to cerebral venous insufficiency caused by an arteriovenous malformation ³² and even in relation to extremes of cranial venous outflow asymmetry, ³³ chronic fatigue syndrome, and fibromyalgia. ^{34 35 36}

Conclusions

We suggest, therefore, that there may be a unifying organic basis to many of the complex symptoms and problems following skull base surgery, including headache and CSF leaks, in the form of iatrogenic compromise to cranial venous outflow. Moreover, we suggest that a CSF leak represents a pathological, but essentially homeostatic, response to raised intracranial pressure in this situation and that while meticulous surgical technique may reduce its incidence, ¹⁴ if cranial venous outflow compromise is left untreated, this may simply mean that one set of symptoms are exchanged for another. ³⁷