Obstructive Hydrocephalus Caused by Tumefactive Perivascular Spaces: A Case Report

Abstract

Patient: Female, 66-year-old

Final Diagnosis: Tumefactive perivascular spaces

Symptoms: Somnolence

Clinical Procedure: —

Specialty: Radiology

Objective: Rare disease

Background

Perivascular spaces (PS), often called Virchow-Robin spaces, are fluid-filled regions surrounding the brain’s blood vessels, typically benign and detected incidentally on MRI scans. However, their enlargement, termed tumefactive PS, is rare and poses significant diagnostic challenges, potentially mimicking severe intracranial conditions. Accurate identification is critical, as these expanded spaces can lead to serious clinical outcomes like hydrocephalus or brain herniation. Misinterpretation of imaging can result in incorrect diagnoses and unwarranted procedures. This case report highlights a rare instance where tumefactive PS caused obstructive hydrocephalus, underscoring the necessity for precise diagnosis.

Case Report

We report a case involving a 66-year-old Hispanic female with a complex medical history, including insulin-dependent diabetes, prior stroke, and post-Whipple’s procedure for pancreatic cancer, who was admitted with progressive somnolence. Initial evaluations indicated encephalopathy. Advanced imaging with CT and MRI identified significantly enlarged PS near the third and fourth ventricles, causing obstructive ventriculomegaly. Differential diagnoses considered cystic tumors and infections, yet MRI findings – cerebrospinal fluid (CSF) isointensity and lack of contrast enhancement – confirmed tumefactive PS. A ventriculoatrial shunt was considered, but the patient’s condition rapidly worsened due to sepsis and an intraperitoneal abscess, culminating in multi-organ failure and death before surgery.

Conclusions

Although rare, tumefactive PS can mimic serious intracranial diseases, necessitating careful MRI evaluation to differentiate these benign spaces from more severe pathologies. Key MRI indicators include alignment with penetrating vessels, absence of enhancement, and CSF signal intensity. Misdiagnosis can lead to unnecessary surgical interventions, emphasizing the importance of accurate imaging interpretation. In symptomatic cases, usually due to mass effect, surgical intervention might be required. Prompt and precise diagnosis is crucial for managing symptomatic tumefactive PS effectively.

Introduction

Perivascular spaces (PVS), also known as Virchow-Robin spaces (VRs), are pial-lined spaces of interstitial fluid that travel surrounding the cerebral vasculature in their course through brain parenchyma. These PS are often asymptomatic, and the surrounding brain is largely unaffected by their presence. When small and only seen on MRI imaging, they may be considered a benign finding.

Rarely, these PVS enlarge and are thus known as tumefactive. The mechanisms leading to tumefactive PVS remain uncertain, with theories suggesting a combination of vascular permeability changes, impaired interstitial fluid drainage, and inflammatory responses [1]. Clinical presentation is quite variable, given that symptoms are mostly secondary to PVS location and mass effect. They are referred to as giant tumefactive PVS (GTPVS) when they are equal to or greater than 1.5 cm [2]. If these spaces enlarge, they can exert a mass effect, resulting in complications such as obstructive hydrocephalus [3]. In cases where hydrocephalus occurs, symptoms may include progressive headaches, gait disturbances, and cognitive impairment [4]. Previous reports of tumefactive PVS have primarily focused on asymptomatic or incidentally found lesions without mass effect. In contrast, our case involved a unique presentation of symptomatic tumefactive PVS with obstructive hydrocephalus. Thus, it is important to recognize this condition and its imaging characteristics to avoid confusion with alternate diagnoses that would result in different management courses.

Our case also differs in that the patient’s clinical presentation was initially attributed to toxic/metabolic encephalopathy due to electrolyte abnormalities and hepatic dysfunction, and only later was the hydrocephalus due to tumefactive PVS recognized on imaging. Failure to correctly diagnose tumefactive PVS can lead to unnecessary biopsies or other neurosurgical interventions [5]. We present a rare and complex case of tumefactive PVS with associated mass effect resulting in obstructive supratentorial hydrocephalus. We present the imaging findings of tumefactive PVS and discuss the differential diagnosis, treatment, and management considerations.

Case Report

A 66-year-old woman who was confined to bed, with a past medical history of stroke, insulin-dependent diabetes mellitus, and pancreatic cancer status post-Whipple’s procedure 4 months ago, presented to the hospital with a 2-week history of progressive confusion and decreased responsiveness. Although the patient reported a prior history of stroke, no imaging evidence of chronic infarction was identified, and there were no documented medical records available to confirm the event. She denied symptoms of headaches, fever, or night sweats. Laboratory studies revealed elevated liver enzymes, AST 77 U/L and ALT 71 U/L, as well as elevated total bilirubin at 10.4 mg/dL and low potassium levels at 2.3 mmol/L, without leukocytosis; the white blood cell count (WBC) was 5000/mm³. A head CT scan revealed well-defined hypodense foci at the left medulla, suggestive of PVS. These cystic structures appeared to extend into the fourth ventricle, exerting a mass effect upon adjacent structures, causing ventricular enlargement, consistent with obstructive hydrocephalus (Figure 1A). A subsequent brain MRI scan confirmed tumefactive PVS in the vicinity of the third and fourth ventricles, resulting in supratentorial obstructive hydrocephalus (Figure 1B–1F). There were no elevated inflammatory markers to suggest an infectious process or encephalomalacia to suggest a prior alternate pathology. Subsequently, the patient was scheduled for ventriculoatrial shunt placement for management. However, less than 1 week later, she developed persistent fevers, increasing lethargy, and global aphasia. Elevated inflammatory markers were noted, including WBC at 14 000/mm³ and blood cultures growing Candida glabrata, Staphylococcus lugdunensis, and Klebsiella pneumoniae, confirming sepsis. An abdominal CT demonstrated an intraperitoneal abscess. Unfortunately, before the shunt placement could be performed, the patient had a rapid clinical deterioration related to her sepsis with an intraperitoneal abscess, causing multi-organ failure and eventual death.

Figure 1.

Axial (A) images of a head CT without IV contrast demonstrate hypodense foci at the left medulla suggestive of PVS. These structures are prominent and appear to be extending into the fourth ventricle, exerting a mass effect upon adjacent structures causing consequent ventricular enlargement, consistent with obstructive hydrocephalus. Axial (B, D–F) and (C) coronal images of a brain MRI with and without IV contrast. T2 WI (B, C), T2 FLAIR (D), contrast-enhanced T1 WI (E), and DWI (F) show a cluster of well-defined T2 hyperintense and T1 hypointense oval-shaped cystic-like lesions, isointense to CSF in all sequences, and demonstrating no associated contrast enhancement. Non-enhancement on post-contrast T1 WI (E) and lack of restricted diffusion on DWI (F) help to rule out abscess or other acute infectious/inflammatory causes. These findings are consistent with enlarged perivascular (Virchow-Robin) spaces (red arrows). There were subsequent obstruction of the cerebral aqueduct with supratentorial obstructive hydrocephalus and transependymal CSF accumulation (yellow arrows). WI – weighted image.

Discussion

Tumefactive PVS are primarily classified according to their location relative to cerebral vasculature, with the least common reported subtype being type 1 (lenticulostriate arteries through the anterior perforated substance) and the most commonly reported subtypes being type 2 (perforating medullary arteries) and type 3 (mesencephalothalamic) [4]. Our case corresponds to a type 3 tumefactive PVS given the lesion’s location at the midbrain near the third and fourth ventricles. Type 3 PVS arises in the mesencephalothalamic region, following the course of penetrating vessels through the midbrain and thalamus, and are often associated with obstructive hydrocephalus when large enough to exert a mass effect [4].

Each subtype has distinct imaging characteristics. Type 1 PVS are typically small and round, seen along the basal ganglia and anterior perforated substance, and are usually asymptomatic [1]. Type 2 PVS occur in the white matter of the high convexities along the path of medullary arteries and are also typically asymptomatic [4]. Type 3 PVS, such as in our case, occurs in the midbrain and perimesencephalic region, and, due to their proximity to the ventricular system, are most likely to become symptomatic, causing obstructive hydrocephalus [4].

The mechanism that causes PVS dilatation is not entirely known, with several theories including increased arterial wall permeability, altered drainage of the brain’s interstitial fluid, and abnormal inflammatory activity [6]. There have also been case reports of presentation following radiation therapy [7]. When located in a typical location following the tract of penetrating vessels, MRI findings are characteristic and may be considered pathognomonic [3,4]. The lesions are round-to-oval, cystic-like, along the trajectory of penetrating vessels, isointense to CSF through all sequences, and have no associated contrast enhancement. In our case, the MRI demonstrated classic features of tumefactive PVS: sharply demarcated, CSF-isointense lesions with no enhancement, no surrounding edema, and an absence of diffusion restriction. These imaging findings, combined with their anatomical location in the third and fourth ventricles, confirmed the diagnosis of type 3 tumefactive PVS.

It is essential to differentiate tumefactive PVS from other cystic brain lesions such as neoplasms, infections, or cystic infarcts, as misdiagnosis can lead to unnecessary surgical interventions. The differential diagnosis for tumefactive PVS includes several cystic intracranial lesions [8]. In our case, the initial imaging findings prompted consideration of cystic neoplasms (eg, pilocytic astrocytoma or hemangioblastoma), infectious processes with cystic components (such as brain abscess), and chronic cystic infarcts or encephalomalacia [8]. However, there were no solid or enhancing components to suggest a neoplasm, and no restricted diffusion to support an abscess. Although a mass effect was present, there was no evidence of infarction or history of trauma that would suggest cystic encephalomalacia [8]. Recognition of these distinguishing imaging features is critical to avoid misdiagnosis and unnecessary surgical interventions.

Management of asymptomatic patients is mostly observation, and imaging follow-up of type 2 PVS appears unnecessary given their typical stability [7]. However, in type 3 PVS with mass effect, patients can present with hydrocephalus and clinical symptoms such as progressive cognitive impairment, headaches, or gait instability, often mimicking other neurological or metabolic disorders [4]. When symptomatic (usually type 3 PVS with hydrocephalus), surgical interventions may be considered, including CSF diversion and endoscopic decompression, with favorable outcomes [4]. Our case shows the importance of early recognition, as a ventriculoatrial shunt may have provided symptomatic relief if the patient’s systemic condition had allowed for timely intervention.

Conclusions

We report a case of a rare presentation of symptomatic tumefactive PVS – a type 3 subtype – located near the third and fourth ventricles, leading to obstructive supratentorial hydrocephalus. Recognizing their characteristic imaging features is crucial to avoid unnecessary invasive procedures. In our case, the diagnosis was supported by MRI findings of CSF-isointense, non-enhancing, well-demarcated lesions without surrounding edema or restricted diffusion. These findings helped distinguish tumefactive PVS from other entities considered in the differential diagnosis, such as cystic neoplasms, infectious cysts, or encephalomalacia. Although the patient was initially scheduled for a ventriculoatrial shunt to alleviate hydrocephalus, her clinical course was complicated by sepsis and multi-organ failure, which precluded surgical intervention. Based on location and size, tumefactive PVS may result in symptoms related to obstructive hydrocephalus or brain herniation. Timely diagnosis and intervention, such as CSF diversion, are critical in symptomatic cases. Further research is warranted to better understand the pathophysiology and optimal management strategies for symptomatic tumefactive PVS.