A Case of Aqueductal Stenosis with Bilateral Papilledema and Abducens Nerve Palsies without Headache

Abstract

Introduction

We report a case of aqueductal stenosis presenting with bilateral papilledema and diplopia, notably without headache.

Case Presentation

A 16-year-old girl with no relevant medical history presented with a 1-week history of binocular diplopia without any loss of visual acuity in either eye. At the time of her visit, she had no symptoms of headache or vomiting. Examination of eye movements revealed bilateral abduction deficits and fundoscopic examination showed bilateral optic disc swelling. Non-contrast computed tomography of the head indicated hydrocephalus. Contrast-enhanced magnetic resonance imaging of the head revealed significant dilatation of the lateral and third ventricles but not in the fourth ventricle. Sagittal T2-weighted imaging with constructive interference in the steady state showed membranous occlusion of the cerebral aqueduct. The patient underwent an endoscopic third ventriculostomy. Binocular diplopia improved during the early postoperative period.

Conclusion

Aqueductal stenosis should be considered in the differential diagnosis for patients presenting with bilateral papilledema and abducens nerve palsies, even in the absence of headache or other neurological findings.

Introduction

The cerebral aqueduct is one of the narrowest areas in the cerebrospinal fluid pathway, making it susceptible to stenosis and obstruction, which can lead to hydrocephalus [1]. Aqueductal stenosis is a condition in which congenital or acquired stenosis causes cerebrospinal fluid stasis, resulting in chronic internal pressure fluctuations and dilation of the upstream lateral and third ventricles. This condition accounts for 6–66% of hydrocephalus cases in children and 5–49% in adults [2]. Here, we report a case of aqueductal stenosis presenting with bilateral papilledema and abducens nerve palsy without headache.

Case Report

A 16-year-old girl presented to the Department of Ophthalmology, Toyokawa City Hospital, with a 1-week history of binocular diplopia. She had no symptoms of headache or vomiting at the time of the initial visit but was previously admitted to the hospital for chronic light-headedness. Her height, weight, body mass index, and blood pressure were 157.0 cm, 59.0 kg, 24.00, and 120/85 mm Hg, respectively. She was not pregnant, had not recently given birth or received vaccinations, and had no family history of thrombosis.

Clinical examination revealed visual acuity of 20/20 and 20/25 in the right and left eyes, respectively, with intraocular pressures of 20 mm Hg bilaterally. Pupillary reflexes were normal, with no afferent pupillary defects. Critical flicker fusion frequencies without attenuation were 36 Hz and 33 Hz in the right and left eyes, respectively. Mild esotropia was noted at near, and the Hess screen test revealed esotropia and bilateral abduction deficits. No abnormalities were observed in the anterior segment of the eyes on slit-lamp microscopy. Still, fundoscopic examination revealed marked redness and swelling of the optic disc in both eyes (shown in Fig. 1). Optical coherence tomography (OCT) confirmed bilateral optic disc swelling with normal macular morphology. The Goldmann visual field test revealed enlarged Marriott blind spots in both eyes. Urgent non-contrast computed tomography (CT) of the head revealed enlarged bilateral lateral and third ventricles without intracranial occupying lesions (shown in Fig. 2a). Contrast-enhanced magnetic resonance imaging (MRI) of the head revealed no apparent neoplastic lesions. Significant ventricular dilatation was also observed in the lateral and third ventricles but not in the fourth ventricle. The cerebral sulci were indistinct. Sagittal T2-weighted imaging with constructive interference in the steady state [3] revealed membranous occlusion in the aqueduct of Sylvius, and membrane-like structures were observed in the aqueduct without contrast enhancement (shown in Fig. 2b). Blood test results, including prothrombin time, activated partial thromboplastin time, D-dimer levels, protein C activity, and protein S activity of the coagulation system, were all normal. Autoantibodies, such as antinuclear and anticardiolipin antibodies, were negative, and no evidence of thrombophilic predisposition was observed.

Fig. 1.

Fundus image at the initial consultation (a) right eye and (b) left eye; bilateral papilledema is visualized.

Fig. 2.

Computed tomography (CT) without contrast of the head and Sagittal of constructive interference in steady state (CISS) T2 magnetic resonance imaging (MRI) of the head (a) CT showing bilateral lateral ventricles and the third ventricle were enlarged. b Sagittal of CISS MRI showing membranous occlusion (arrow).

Based on these findings, the patient was diagnosed with aqueductal stenosis and consequent intracranial hypertension and bilateral abducens nerve palsies. She was admitted to the Department of Neurosurgery and underwent endoscopic third ventriculostomy (ETV). A neuroendoscope was inserted into the right lateral ventricle, and the enlarged third ventricle of the foramen of Monroe was observed directly below. The thinning grayish-white ridge of the third ventricle (shown in Fig. 3a) was punctured with forceps and opened with a balloon catheter (shown in Fig. 3b) to confirm the flow (shown in Fig. 3c). The cerebral aqueduct was pinhole-shaped, slightly open, and near occluded (shown in Fig. 3d). One week posttreatment, binocular diplopia improved. Postoperative MRI showed reduced ventricular size and clear sulci.

Fig. 3.

Endoscopic operative view. a The floor of the third ventricle was stretched. b Perforation of the third ventricle floor by clamp and balloon. c Post-endoscopic third ventriculostomy. d The cerebral aqueduct is constricted to a pinhole.

Six months after discharge, the papilledema was reduced, and OCT findings also improved. Her visual acuity was 20/20 bilaterally, with no headache, or other symptoms of intracranial hypertension.

Discussion

Congenital hydrocephalus occurs in 1 in 1,000 live births, two-thirds of which are due to aqueductal stenosis. Although aqueductal stenosis is generally thought to occur in childhood, it is often overlooked in children because of ambiguous complaints [4].

Milhorat classified congenital mesencephalic aqueduct stenosis into four morphopathological types: (1) forking, (2) gliosis, (3) simple primary stenosis (true narrowing), and (4) septum formation [5]. In this case, neuroendoscopic findings revealed no membranous septum or strut formation in the cerebral aqueduct but stenosis due to membrane-like structures. The cerebral aqueduct opened in a pinhole-like fashion. The patient had no history of meningitis or encephalitis, and no apparent cause was identified; however, if aqueductal stenosis was considered congenital, it was inferred that this case falls into the category of (2) gliosis or (4) septum formation.

Late-onset hydrocephalus associated with aqueductal stenosis has been reported as panventriculomegaly [6], long-standing overt ventriculomegaly in adults [7], late-onset idiopathic aqueductal stenosis [8], and late-onset aqueductal membranous occlusion (LAMO) [9]. Most late-onset hydrocephalus cases occur before the age of 60, with headaches due to intracranial hypertension in patients under 50 years old [9]. In this case, panventriculomegaly was excluded because there was no family history and no evidence of downward displacement of the floor of the third ventricle or membranous structures of the anterior bridge alveolus, and long-standing overt ventriculomegaly in adults was excluded because macrocephaly had not been previously noted. Although it is challenging to distinguish late-onset idiopathic aqueductal stenosis from LAMO based on clinical presentation alone, this case was diagnosed as LAMO based on endoscopic findings of membranous structures in the cerebral aqueduct.

Patients with hydrocephalus often present with symptoms of intracranial hypertension, such as headache, nausea/vomiting, transient visual obscurations, and enlargement of head circumference [10]. However, in aqueductal stenosis, symptoms repeatedly appear and subside intermittently as the intracranial pressure rises and falls [7]. In this case, the patient presented with only binocular diplopia and no headache or vomiting during the outpatient visit. However, a chronic, mild headache had been reported previously. The abducens nerve takes an angular course over the clivus through Dorello’s canal, making it more susceptible to mechanical stresses such as intracranial pressure fluctuations and arteriosclerosis, resulting in abducens nerve palsy [11]. Hydrocephalus can cause impaired venous return, leading to increased intracranial pressure. Moreover, esotropia and bilateral abduction deficits are believed to result from the same mechanism. Therefore, when bilateral abducens nerve palsies are accompanied by bilateral papilledema, intracranial hypertension should be considered, even in the absence of headaches or other neurological findings.

The sagittal section of the MRI constructive interference in the steady state [3] image is essential for diagnosing hydrocephalus caused by the cerebral aqueduct, as it can differentiate between morphology and pathology. In this case, the third and lateral ventricles were enlarged on the head MRI, but the fourth ventricle was normal.

Treatment options for aqueductal stenosis include ventriculoperitoneal shunting, endoscopic aqueductoplasty, and ETV. ETV has recently become the first-choice treatment for noncommunicating hydrocephalus caused by aqueductal stenosis, with higher success rates reported in hydrocephalus caused by aqueductal stenosis than in that caused by tumors or cystic lesions [12]. However, there is a risk of basilar artery injury that requires careful opening. Although endoscopic aqueductoplasty has also been performed for membranous obstruction of the cerebral aqueduct, it is sometimes combined with ETV and was not selected in this case because restenosis was observed in 88.2% of the patients [13].

In children, symptomatic complaints are often vague, causing chronic, slowly progressive obstructive hydrocephalus to go unnoticed and overlooked. Slowly increasing intracranial pressure is often seen in younger patients and may present as a chronic low-grade nonspecific headache, as observed in this case [14]. Prolonged papilledema can lead to optic atrophy [15] and irreversible visual impairment, necessitating prompt relief of intracranial hypertension. Rapid diagnosis and therapeutic intervention are crucial in cases of acute-onset, rapidly progressive cerebral herniation, which can lead to severe deterioration of the general condition.

Intracranial hypertension is often associated with headache and vomiting; however, when bilateral papillary edema and abducens nerve palsy are present without headache, as in this case, hydrocephalus associated with aqueduct stenosis should also be considered in the differential diagnosis. The CARE Checklist has been completed by the authors for this case report and is attached as online supplementary material (for all online suppl. material, see https://doi.org/10.1159/000542582).

Acknowledgments

We thank Dr. Yuto Sakakibara and Dr. Mitsuharu Yamamoto of the Department of Neurosurgery, Toyokawa City Hospital for providing the endoscopic images. We would like to thank Editage (www.editage.com) for the English language editing.

Statement of Ethics

This study was conducted in accordance with the Declaration of Helsinki of the World Medical Association. The study protocol was reviewed and the need for approval was waived by the Ethics Committee of Toyokawa City Hospital. Written informed consent was obtained from the parent for publication of the details of their medical case and any accompanying images.

Conflict of Interest Statement

The authors have no conflicts of interest to declare.

Funding Sources

This study was not supported by any sponsor or funder.

Author Contributions

D.N.: patient examination, clinical data collection, and writing – original draft; H.O. and T.D.: patient examination and clinical data collection; Y.S. and A.T.: writing – editing; M.H. and Y.I.: writing – review. All the authors have read and approved the final version of this manuscript.

Funding Statement

This study was not supported by any sponsor or funder.

Data Availability Statement

All data generated or analyzed during this study are included in this article and its online supplementary material. Further inquiries can be directed to the corresponding authors.