Papilledema in NF2-related Schwannomatosis without Ventriculomegaly and Overt Intracranial Hypertension: A Case Series and Literature Review

Abstract

Neurofibromatosis 2-related schwannomatosis is a rare genetic disorder marked by the development of multiple central nervous system tumors and, occasionally, non-hydrocephalic intracranial hypertension. This report details two cases of papilledema in patients with neurofibromatosis 2-related schwannomatosis, characterized by normal ventricular morphology on Magnetic resonance imaging and refractory to conservative treatment. Both patients-a 23-year-old and a 31-year-old female-demonstrated complete resolution of papilledema and restoration of visual function following ventriculoperitoneal shunt placement. These cases underscore the critical role of early ventriculoperitoneal surgical intervention in mitigating vision loss and emphasize the necessity for rigorous clinical surveillance in this unique patient population.

Introduction

Neurofibromatosis type 2 (NF2), also known as NF2-related schwannomatosis (NF2-SWN),¹⁾ is a rare autosomal dominant disorder characterized by the development of multiple central nervous system tumors, most notably bilateral vestibular schwannomas (VS), along with meningiomas and ependymomas.^2-4) Hydrocephalus, a frequent complication, often arises from tumor-induced obstruction of the ventricular system or disruptions in cerebrospinal fluid (CSF) dynamics.^5,6) In contrast, non-hydrocephalic intracranial hypertension (ICH) represents an atypical and diagnostically challenging presentation, where elevated intracranial pressure (ICP) occurs without ventricular dilation.^7,8) Papilledema, a cardinal manifestation of ICH, significantly increases the risk of irreversible visual impairment, even in cases with normal ventricular morphology.⁹⁾ This report examines two cases of NF2-SWN with papilledema without ventriculomegaly, emphasizing the critical need for early recognition and timely intervention to mitigate vision-threatening complications.

Case Reports

Case 1

A 23-year-old female presented with left-sided hearing loss at 13 years of age. The subsequent intracranial evaluation confirmed the diagnosis of NF2-SWN based on the identification of bilateral VS. At 19 years of age, she underwent gamma-knife radiosurgery targeting the vestibular schwannoma, followed by surgical resection of left and right trigeminal schwannomas at 21 and 22 years of age, respectively.

By age 23, the patient developed progressive visual decline, initially in the right eye and subsequently in the left, in the absence of headache or nausea. Funduscopic examination revealed bilateral papilledema (Fig. 1A and B). Preoperative best-corrected visual acuity (BCVA) was no light perception in the right eye and 20/67 in the left eye. Magnetic resonance imaging (MRI) demonstrated multiple cranial nerve tumors and meningiomas (Fig. 1C-E), with no evidence of tumor growth or ventricular dilation. Spinal MRI revealed extensive schwannomas throughout the cervical, thoracic, and lumbar regions, while T2-weighted MRI identified right intraorbital optic nerve edema (Fig. 1F). Cerebral angiography showed hypoplasia of the right transverse sinus without abnormalities in the superior sagittal sinus or cortical venous reflux (Fig. 1G and H), suggesting possible venous outflow obstruction. Compensatory mechanisms, however, appeared well-developed, mitigating significant outflow obstruction contributing to ICH.

Fig. 1

Preoperative fundus and MRI findings in case 1 demonstrate bilateral papilledema and multiple intracranial tumors. (A, B) Preoperative fundus examination revealed pronounced bilateral papilledema. (C-E) Preoperative MRI identified multiple cranial nerve tumors and meningiomas, with no evidence of tumor progression or ventricular enlargement. (F) T2-weighted MRI revealed edema in the intraorbital segment of the right optic nerve. (G) Right cerebral angiography (anterior-posterior view) demonstrated hypoplasia of the right transverse sinus without abnormalities in the superior sagittal sinus or evidence of delayed venous drainage. (H) Left cerebral angiography (anterior-posterior view) showed no abnormalities in the superior sagittal sinus or other venous outflow pathways indicative of obstruction.

MRI: magnetic resonance imaging

Initial treatment with steroid pulse therapy for bilateral optic nerve edema and transcranial decompression of the right optic nerve canal yielded no improvement. Given the clinical suspicion of elevated ICP despite the absence of ventriculomegaly, a ventriculoperitoneal (VP) shunt was placed. Stereotactic ventriculocentesis, conducted to address slit-like ventricles, revealed an opening pressure of 15 cm H₂O. Two weeks after VP shunt placement, the patient experienced rapid resolution of papilledema (Fig. 2A and B), and BCVA improved to hand-motion detection at 30 cm in the right eye, while the left eye remained stable at 20/67 without further deterioration.

Fig. 2

Postoperative fundus findings demonstrating resolution of bilateral papilledema. (A, B) Postoperative fundus examination confirmed complete resolution of bilateral papilledema.

Case 2

A 31-year-old female initially presented with gait disturbance at 9 years of age, which led to the diagnosis of NF2-SWN following the surgical resection of a thoracic schwannoma and meningioma. Subsequent intracranial imaging confirmed the presence of bilateral VS, consistent with NF2-SWN. By 26 years of age, she experienced progressive left-sided hearing loss, which ultimately progressed to profound bilateral deafness by 30 years of age.

At 31 years of age, routine ophthalmological evaluation revealed bilateral papilledema without headaches or nausea (Fig. 3A and B). The patient had no subjective visual impairments at the time of presentation. Preoperative BCVA was 20/50 in the right eye and 20/20 in the left eye. MRI revealed slight enlargement of the left VS and a falx meningioma (Fig. 3C and D) but no evidence of ventricular dilation (Fig. 3E). A spinal MRI revealed extensive schwannomas extending from the cervical to the lumbar spine.

Fig. 3

Preoperative imaging and ophthalmologic findings in case 2 illustrate bilateral papilledema. (A, B) Preoperative fundus examination revealed significant bilateral papilledema. (C-E) Preoperative MRI depicted multiple tumors involving cranial nerves and meningiomas, with no evidence of tumor progression or ventricular dilation.

MRI: magnetic resonance imaging

Given the successful management of a similar presentation in case 1, a VP shunt was placed for suspected elevated ICP. Stereotactic ventriculocentesis revealed an opening pressure of 20 cm H₂O. CSF analysis showed normal protein levels and no pleocytosis, suggesting no inflammatory or obstructive pathology. The papilledema resolved completely within 3 months postoperatively, and the BCVA remained stable (20/50 in the right eye and 20/20 in the left eye).

Discussion

This report of two cases of NF2-SWN highlights the potential for significant papilledema and vision loss, even in the context of borderline ICP measurements (15-20 cmH₂O) and normal ventricular morphology on imaging. The rapid resolution of papilledema following VP shunt placement strongly implicates chronic ICH as the predominant mechanism. This finding underscores the necessity of maintaining a high index of suspicion for elevated ICP in patients with NF2-SWN presenting with unexplained visual disturbances, even when initial imaging and ICP measurements appear unremarkable or only marginally elevated.¹⁰⁾

The development of papilledema despite normal ICP measurements in case 1 (15 cm H₂O) and case 2 (20 cmH₂O) may reflect the slow growth of tumors in NF2-SWN, allowing intracranial adaptations that mask acute symptoms like headache or vomiting.¹¹⁾ Mechanisms such as CSF redistribution and reduced brain parenchymal volume may transiently counteract the effects of elevated ICP.¹²⁾ However, even mild chronic elevation in ICP can exert sufficient pressure on the optic nerve head, culminating in papilledema.^13,14) The resolution of papilledema after VP shunting further supports the hypothesis that subtle, chronic ICP elevations are sufficient to compress the optic nerve. Notably, ventriculocentesis opening pressure measurements provide only a snapshot of ICP, potentially underestimating dynamic fluctuations over time.

The pathophysiology of elevated ICP without ventriculomegaly in NF2-SWN is multifactorial, involving tumor burden, impaired CSF flow, venous outflow obstruction, and inflammation.^12,15-19) These mechanisms create a cumulative mass effect, compressing brain tissue and exacerbating ICH.^20-23) Comparable conditions, such as idiopathic ICH, highlight venous sinus stenosis as a potential target for treatment, including shunt surgery.²⁴⁾ Evidence suggests that parasagittal meningiomas causing superior sagittal sinus narrowing can provoke comparable pathophysiological changes.²⁵⁾ Accordingly, in cases such as case 1, the absence of venous perfusion disturbances, including those within the superior sagittal sinus, should be explicitly highlighted in clinical discussions to refine diagnostic considerations.

Case 1 demonstrates how multiple factors contribute to elevated ICP in NF2-SWN. The presence of multiple intracranial tumors, including schwannomas and meningiomas, likely disrupted CSF dynamics or venous outflow, leading to mild but chronic ICP elevation. Although these pressure elevations were insufficient to cause ventricular dilation, they imposed enough mechanical stress to damage the optic nerve head. Cerebral angiography in case 1 revealed a hypoplastic right transverse sinus with preserved venous drainage, suggesting additional factors such as hyperproteinorrhachia,⁶⁾ localized blockages, or chronic inflammation may underlie the "non-hydrocephalic" form of ICP elevation. Furthermore, the optic nerve edema observed in case 1 indicates localized cerebral edema, likely exacerbating ICP by altering regional CSF dynamics. These findings underscore the interplay between CSF protein dynamics, venous anatomy, and brain parenchymal properties in the pathophysiology of ICH without ventricular enlargement in NF2-SWN patients.

A review of 12 published cases (Table 1) highlights the limitations of using ventricular size alone to assess elevated ICP in NF2-SWN and sporadic VS.^7,8,26-31) Although sporadic cases often involve hyperproteinorrhachia,⁶⁾ NF2-SWN is characterized by multiple tumors with distinct pathophysiological mechanisms. Conversely, NF2-SWN typically involves multiple tumors with distinct biological characteristics, necessitating individualized evaluation. Despite these differences, any papilledema in a VS context warrants comprehensive assessment for ICH, irrespective of ventricular size or ICP readings.⁹⁾ In younger patients, papilledema may precede ventriculomegaly and serve as an early indicator of elevated ICP, requiring timely intervention to avert vision loss.^32-34)

Table 1

Summary of cases of papilledema without ventricular dilation associated with vestibular schwannomas

Author & Year	Age (years), sex	NF2-SWN	VS laterality	Intracranial meningioma	Venous sinus stenosis/occlusion	Ventricular size	Treatment	Papilledema resolu tion	Initial ICP (measured site)	Notes
CSF: cerebrospinal fluid; ICP: intracranial pressure; LP: lumboperitoneal; NF2-SWN: neurofibromatosis type 2-related schwannomatosis; ONSF: optic nerve sheath fenestration; VP: ventriculoperitoneal; VS: vestibular schwannoma
Harada et al., 1998	26, Male	Yes	Bilateral	No	No	Normal	1st: tumor removal 2nd: VP shunt	No	Not mentioned	Optic atrophy developed despite shunt
Thomas et al., 1999	31, Male	Yes	Bilateral	Yes	No	Normal	1st: ONSF (right) 2nd: LP shunt	No	32 cmH2O (lumbar puncture)	Optic atrophy developed despite shunt
Grainger et al., 2005	56, Male	No	Left	Not reported	Not reported	Normal	Tumor removal	Yes	14 cm H2O (ventricular puncture)	High CSF protein (basal cistern)
Matos et al., 2016	64, Male	No	Right	Not reported	Not reported	Normal	Tumor removal	Yes	Not mentioned
Candanedo et al., 2017	20, Female	No	Right	Not reported	Not reported	Normal	Tumor removal	Yes	Not mentioned	Enlarged sella
Jefferis et al., 2019	Case 1 / 23, Female	No	Left	No	No	Normal	ONSF (bilateral)	Yes	Not mentioned
	Case 2 / 23, Female	No	Right	No	No	Normal	1st: ONSF (bilateral) 2nd: Tumor removal	Yes	Not mentioned
	Case 3 / 54, Male	No	Left	No	Yes	Normal	1st: tumor removal 2nd: ONSF (bilateral)	Yes	Not mentioned
Ronan et al., 2020	24, Female	No	Right	Not reported	No	Normal	Tumor removal	Yes	21 cm H2O (lumbar puncture)	High CSF protein (lumbar cistern)
Gavotto et al., 2022	39, Male	No	Right	Not reported	No	Normal	Tumor removal	Yes	18 cm H2O (lumbar puncture)	High CSF protein (lumbar cistern)
Present cases (Ito et al.)	Case 1 / 23, Female	Yes	Bilateral	Yes	Yes	Normal	1st: optic canal decompression 2nd: VP shunt	Yes	15 cm H2O (ventricular puncture)	Multiple schwannomas, meningiomas
	Case 2 / 31, Female	Yes	Bilateral	Yes	No	Normal	VP shunt	Yes	20 cm H2O (ventricular puncture)	Multiple schwannomas, meningiomas

Within this case series, two contrasting sets of factors appeared to determine the final visual outcomes. First, those associated with persistent visual loss include: (i) delayed treatment until optic disk edema becomes chronic, culminating in secondary optic atrophy; (ii) advanced visual field deficits, including central vision impairment; and (iii) inadequate long-term control of either the tumor or elevated ICP. Harada et al.⁷⁾ described a patient with NF2 who exhibited severe optic disk edema, ultimately declining to hand-motion vision despite VP shunting. This finding underscores that once papilledema is prolonged and secondary atrophy is established, the likelihood of meaningful visual recovery diminishes. In contrast, other reports have highlighted that early intervention is critical for preserving or restoring vision, describing timely tumor resection or CSF shunting to lower ICP before irreversible optic nerve fiber damage occurs, thereby leading to papilledema resolution and stable or improved visual acuity.^28,30) Furthermore, timely recognition of mild visual field deficits facilitates rapid treatment and favorable outcomes, as evidenced in a young patient whose papilledema resolved completely following early surgical decompression.²⁶⁾ The presence of optic nerve edema on T2-weighted MRI, as observed in case 1, may serve as an early indicator of reversible visual impairment that warrants urgent intervention. Additional investigations are required to identify reliable prognostic markers of visual recovery in patients with NF2-SWN-associated papilledema.

Given the insidious nature of ICH in NF2-SWN, regular ophthalmologic evaluations, including fundoscopic examinations, are essential for early detection of papilledema and prevention of vision loss. Previous studies on ICH recommend ophthalmologic monitoring every 6 months, depending on the disease severity.³⁵⁾ In patients with asymptomatic NF2-SWN, annual ophthalmologic evaluations may be sufficient, whereas those with progressive tumors, prior papilledema, or other risk factors for ICH may require examinations every 6 months. Although specific guidelines for NF2-SWN-related papilledema are lacking, such recommendations are consistent with general management strategies for papilledema and ICH in similar conditions, such as idiopathic ICH.³⁵⁾

Continuous ICP monitoring is a valuable tool for assessing dynamic fluctuations in ICP and has been proposed as a method to confirm ICH before VP shunting. In certain clinical scenarios, such as when symptoms are ambiguous or when distinguishing idiopathic ICH from tumor-related ICP elevations, ICP monitoring can aid in treatment decisions.³⁶⁾ However, in patients with NF2-SWN with documented progressive papilledema and visual deterioration, as observed in our cases, delaying intervention for prolonged ICP monitoring may increase the risk of irreversible vision loss.

The decision to perform VP shunting should be guided primarily by clinical findings and ophthalmologic assessments rather than relying solely on ICP measurements, which may underestimate chronic or intermittent elevations.³⁷⁾ In our cases, despite borderline opening pressures (15-20 cm H₂O), papilledema and vision loss improved significantly after VP shunting, suggesting that even mild chronic ICP elevation can be clinically significant. Therefore, although ICP monitoring remains an option in selected cases, early surgical intervention should be prioritized in patients with progressive papilledema and deteriorating vision.

Timely VP shunt placement is critical for preventing vision loss in NF2-SWN patients with elevated ICP.^13,38) The significant visual recovery in both cases underscores its effectiveness as a primary intervention. Alternative options, such as tumor resection or optic nerve sheath fenestration, may be considered in selected cases, particularly when VP shunting is contraindicated or ineffective.³⁹⁾ Preoperative MRI of optic nerve sheath dilation can guide surgical decisions, though intervention should not be excluded based solely on its absence.⁴⁰⁾ Treatment strategies must be tailored to the clinical presentation, neuroimaging findings, and the relative risks and benefits of various interventions.

In conclusion, these cases highlight that NF2-SWN can result in chronic ICH and papilledema, even with borderline ICP and no ventriculomegaly. Early detection through regular ophthalmologic monitoring and prompt VP shunt placement is essential to prevent irreversible vision loss. Clinicians must remain vigilant for papilledema, as even mild ICP elevation may signify significant ICH.

Acknowledgments

The authors thank Dr. Keita Suzuki for his invaluable assistance with data collection.

Informed Consent

Informed consent was obtained from all the patients included in this case report, ensuring adherence to ethical guidelines.

Disclaimer

Author Ryuta Saito is one of the Editorial Board members of the Journal. This author was not involved in the peer-review or decision-making process for this paper.

Conflicts of Interest Disclosure

The authors declare that they have no conflicts of interest. All authors have completed and submitted online self-reported Conflicts of Interest Disclosure Statement Forms to the Japan Neurosurgical Society website in compliance with journal requirements.

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