Adult bilateral idiopathic occlusion of foramina of Monro: is foraminoplasty really safe and effective?

Abstract

Idiopathic bilateral occlusion of foramina of Monro is an extremely rare condition in adults and only few cases are reported. Currently, foraminoplasty is indicated as first-line treatment. We reported the case of a 52-year-old woman who presented with headache, instability and urinary incontinence. The imaging demonstrated bilateral occlusion of foramina of Monro and consequent biventricular hydrocephalus. A ventriculo-peritoneal shunt allowed to treat the hydrocephalus, but it was necessary to remove it for the appearance of peritonitis from salpingitis. Since the initial symptomatology reappeared, according to the literature, we performed an endoscopic foraminoplasty with septostomy. The patient immediately developed short-term memory impairment and subsequently we observed the hydrocephalus recurrence. The positioning of a ventriculo-atrial shunt allowed to improve the symptoms, but the memory remained impaired. In case of bilateral true stenosis of foramina of Monro, foraminoplasty may lead to severe memory impairment. Therefore, cerebrospinal fluid shunting should be considered as an effective and safer treatment.

Background

Currently, foraminoplasty is considered the treatment of choice in case of idiopathic occlusion of foramina of Monro. Nevertheless, the literature is based only on few cases and the resulting advices appear too weak.¹

We documented a possible complication of endoscopic foraminoplasty in a case of bilateral true stenosis of foramina of Monro. We speculate that ventriculo-peritoneal shunt should be considered as a valid alternative treatment in order to avoid severe memory impairment.

Case presentation

A 52-year-old woman presented for the appearance of progressively increasing headache, postural instability and urinary incontinence. The cerebral MR demonstrated the presence of a biventricular hydrocephalus caused by bilateral occlusion of foramina of Monro (figure 1A–C).

Figure 1.

Cerebral MR. Axial (A), coronal (B) and sagittal (C) views of the biventricular hydrocephalus due to bilateral occlusion of foramina of Monro.

We decide to treat the patient through septostomy and endoscopic third ventriculostomy (ETV) but during the procedure, we noticed the presence of complete bilateral stenosis of foramina of Monro that did not allow to safely achieve the third ventricle. Therefore, we performed a ventriculo-peritoneal shunt that allowed to treat the hydrocephalus (figure 2) and consequently to improve the symptoms. After 3 months, it was necessary to remove the shunt for the evidence of peritonitis from left salpingitis. Afterwards, the patient showed the initial symptomatology due to biventricular hydrocephalus recurrence.

Figure 2.

Cerebral CT scan performed after the ventriculo-peritoneal shunt. Surgery allowed to solve the hydrocephalus and to achieve a significant clinical improvement.

According to literature, we decided to perform an imaging-navigated endoscopic foraminoplasty. The right lateral ventricle was cannulated in order to reach the right foramen of Monro (FM) (figure 3A–B). The fenestration was then widened through Fogarty balloon catheter inflation (figure 3C) allowing to reach the third ventricle floor (figure 3D).

Figure 3.

Endoscopic view of the foraminoplasty. In the right ventricle, we observed a complete occlusion of the foramen of Monro (A). Therefore, through neuronavigation, we identified the anatomical landmarks to get into the third ventricle. We used a Fogarty balloon catheter to perform a fenestration (B) and through its inflation (C), we widened the ventriculostomy. We suppose a fornix stretching as cause of the subsequent memory impairment. Finally, we observed the third ventricle floor (D).

In the immediate postoperative period, the patient developed significant short-term memory impairment documented by neuropsychological evaluation. After 2 months, headache, postural instability and urinary incontinence reappeared.

Investigations

The cerebral CT scan allowed to show that the symptoms were due to the recurrence of the biventricular hydrocephalus (figure 4).

Figure 4.

The cerebral CT scan performed 2 months after foraminoplasty showed the recurrence of the biventricular hydrocephalus.

Differential diagnosis

Clinical, laboratory and radiological investigations excluded the presence of other cerebral complications or systemic events.

Treatment

Since the failure of the endoscopy procedure and the previous peritonitis, we performed a ventriculo-atrial shunt. The postoperative cerebral CT showed the resolution of the biventricular hydrocephalus (figure 5).

Figure 5.

Cerebral CT scan performed after ventriculo-atrial shunt. The cerebrospinal fluid shunting allowed to treat the hydrocephalus and to improve the symptoms, except the memory impairment.

Outcome and follow-up

After the procedure, a substantial improvement of headache, postural instability and urinary incontinence was observed. The clinical improvement with hydrocephalus resolution remained steady over time. On the other hand, the neuropsychological evaluation performed after 6 months reported only a slight improvement of the short-term memory impairment.

Discussion

The occlusion of foramina of Monro is a rare occurrence. While in children or young adults, this condition may be due to congenital closure with monoventricular or biventricular hydrocephalus, in adults, bilateral hydrocephalus is mainly caused by tumours or inflammatory conditions.

The literature classified adult idiopathic bilateral occlusion of foramina of Monro (AIOFM) in four groups, including bilateral true stenosis of the FM, bilateral membrane occlusion of FM, unilateral true FM with septum deviation and unilateral membrane occluding FM with septum deviation.¹ According to this classification, our case should be considered a bilateral true stenosis of FM (Type 1).

In literature, only few cases of AIOFM were described and the treatment of choice was first an endoscopic procedure with unilateral perforation-dilatation of right FM (foraminoplasty), sometimes associated with septum pellucidum fenestration and subsequently, in case of failure, the positioning of a cerebrospinal fluid shunt. The advantages of the foraminoplasty compared with a shunt surgery are quite intuitive, such as avoiding of mechanical problems and malfunction, foreign body reaction, decubitus, breakage, overdraining and shunt revisions.

In all cases previously reported, no complication due to endoscopic procedure was mentioned, despite some authors emphasise the risk of injury to the fornix.¹ We report a case of a patient who developed short-term memory impairment after endoscopic septostomy and right foraminoplasty. This condition was only partially resolved with the positioning of a ventriculo- atrial shunt.

Fornix belongs to the limbic system, a network of cortical and subcortical centres and white matter tracts that modulate memory, emotions and behaviour. The fornix is a group of axons with cell body located in the hippocampus and terminating in the mammillary bodies and it has an important role in memory processes connecting the hippocampus and the thalamus. It is located on the midline, surrounding the thalami and it is composed by a body, crus fornicis, two anterior and two posterior columns. The posterior column of fornix delineates with the anterior pole of the thalamus the foramina of Monro.²

Several studies on human fornix have demonstrated a memory loss if the fornix is damage, although the exact pattern of memory impairment is not completely clear yet. Some studies described an acute amnestic syndrome with anterograde amnesia after isolated bilateral anterior fornix infarction^{3 4} or after systemic rheumatological disease with isolated hippocampal damage.⁵

In our case, we decided to perform as first-line treatment an ETV but, because of true stenosis of foramina of Monro and the absence of clear visualisation of anatomical landmarks, we preferred to implant a ventriculo-peritoneal shunt, subsequently removed after few months for onset of salpingitis. After shunt removing, the patient showed the initial symptoms, namely headache, postural instability and incontinence. Therefore, we decided to perform an imaging- navigated endoscopic right foraminoplasty with septostomy.

After surgery, the patients presented a severe short-term memory loss, with impossibility to perform daily actions, such as shopping or go out independently. The memory impairment was confirmed by neuropsychological evaluation. There was a partial resolution of headache and gait instability. Nevertheless, after 2 months, all the symptoms reappeared.

We initially attributed all the symptoms to a re-occlusion of the foramen on Monro and, considering the endoscopic procedure ineffective we decided to proceed with a ventriculo-atrial shunt. Six months after shunt positioning, CT scan show a complete resolution of the hydrocephalus, but memory remained significantly impaired.

In our opinion, in case of bilateral true stenosis of foramina of Monro, foraminoplasty and septostomy should be avoided. Endoscopic procedures should be reserved in the presence of favourable anatomy.⁶ Otherwise cerebrospinal fluid shunting may represent a valid alternative in order both to avoid fornix damage and to avoid a second surgery in case of foraminoplasty failure.

Learning points.

• Idiopathic stenosis of foramina of Monro is a rare cause of hydrocephalus and there are two main options of treatment: foraminoplasty or cerebrospinal fluid shunting.

• The endoscopic foraminoplasty for the type 1 of adult idiopathic bilateral occlusion of foramina of Monro increases the risk of fornix injury with consequent short-term memory impairment.

• In case of true bilateral stenosis of foramen of Monro, cerebrospinal fluid shunting ensures an effective treatment without risks of fornix injury.