Late-onset idiopathic aqueductal stenosis (LIAS)

LIAS can result in hydrocephalus and typically presents in young adults as headaches. While ventriculography was the standard diagnostic tool used when LIAS was first described, advances in imaging techniques and specifically the advent of magnetic resonance imaging (MRI) allowing clearer visualization of the cerebral aqueduct has resulted in easier diagnosis of LIAS [1,2]. Typically, there is no pathognomonic sign for LIAS, but it is generally associated with a “small fourth ventricle” and cine MR imaging has been shown to be sensitive for blockage of cerebrospinal fluid (CSF) flow at the cerebral aqueduct [3,4]. One study reported that cine imaging was useful in cases of mild hydrocephalus, but reported that seven out of nine patients with significant dilation of the ventricles demonstrated CSF flow at the cerebral aqueduct. The pathophysiologic mechanism in LIAS patients is attributed to partial obstruction with minimal flow through the aqueduct, because a complete obstruction would present with symptomatology that is more rapid and severe. In terms of treatment, CSF drainage via a shunt was the primary modality used when LIAS was first described; however, advances in neuroendoscopy and specifically third ventriculostomy have slowly changed the treatment method of choice [5–7].

The syndrome of longstanding overt ventriculomegaly (LOVA) and the syndrome of hydrocephalus in young and middle-aged adults (SHYMA)

The syndrome of longstanding overt ventriculomegaly describes the association of congenital aqueductal stenosis with headaches and macrocephaly. SHYMA is a clinical syndrome affecting young and middle-aged adults and is associated with either decompensated hydrocephalus, acquired hydrocephalus, or idiopathic hydrocephalus [8]. Age appears to be the main determinant of the clinical syndrome. While the primary symptoms are similar to those of NPH, the main predicament of these patients is the impact on their everyday functional activities in spite of the subtlety of their symptoms. These patients most often have difficulty in performing job-related tasks, with some clumsiness, difficulty with uneven surfaces, and difficulty with stairs in the context of notably absent gait ataxia. In terms of urinary symptoms, patients with SHYMA in Cowan et al.’s study [8] often complained of urinary urgency or frequency but stated that urinary incontinence was rare. The most consistent symptom in this cohort was headache, which was present in 70% of patients. In terms of functional activities, almost 84% of patients in this series reported job performance impairment before a diagnosis was made, with many of these patients facing disciplinary action or job loss. The duration of their symptoms was on average almost 6 years. The majority of patients with SHYMA benefited from surgical intervention, either third ventriculostomy or CSF shunting, with 93% of patients showing at least partial improvement and 56% of patients demonstrating complete recovery. While 29 underwent primary shunting, and 11 underwent third ventriculostomy, interestingly, 6 of the 11 third ventriculostomy patients ultimately required a shunt [8] (Figure 21.2).

Figure 21.2 T2-weighted images in the coronal and sagittal planes. Note the patent endoscopic third ventriculostomy (ETV) and the normal shape of the third ventricle after the ETV.

Hydrocephalus and malignancies

Hydrocephalus secondary to malignancy is a common phenomenon that occurs in adults and children, alike. Patients can present initially with signs and symptoms of hydrocephalus, which prompts radiological imaging that leads to the diagnosis of the underlying tumor. It is estimated that greater than 50% of pediatric patients with brain tumors also have associated hydrocephalus [9]. In this subset of patients almost 95% of pediatric brain tumor patients had obstructive hydrocephalus, with the remainder being communicating hydrocephalus. Greater than 90% of these patients presented with hydrocephalus at diagnosis [9]. Blockage of CSF can occur at several levels depending on tumor location. Cerebral hemisphere tumors, thalamic tumors, tumors of the sellar region, and tumors in the region of the third ventricle can cause blockage on one or both sides of the foramen of Monro, whereas thalamic neoplasms, pineal region tumors and midbrain tumors can block the foramen of Monro or the cerebral aqueduct (Figure 21.3). At the level of the posterior fossa, blockage of the fourth ventricle can lead to obstructive hydrocephalus.

Figure 21.3 This 48-year-old woman presented with an episode of loss of consciousness and work-up in the emergency department demonstrated hydrocephalus secondary to a large mass involving the thalamus. The patient was well until 10 days prior when she began experiencing frequent, severe headaches, of which she had no prior history. MRI TE and T1-weighted images with contrast enhancement show a centrally necrotic, peripherally enhancing nodule within the ventricle, heterogeneous, prominently T2 hyperintense, component of the mass within the right anteromedial and midmedial thalamus, vasogenic edema and infiltrating tumor within the right striatocapsular region, leftward convex bowing of the third ventricle which is slit like, and dilation of the lateral ventricles. Pathological examination of the surgical specimen revealed an infiltrating astrocytoma.

In contrast, communicating hydrocephalus is thought to occur in the context of increased CSF production, such as in the case of choroid plexus tumors (Figure 21.4) [9], or impaired CSF absorption, secondary to leptomeningeal disease or tumor bleeding. Carcinomatous meningitis is associated with various tumor types, including lung and breast cancer metastases. Liaw et al. reported that hydrocephalus was present in 62% of such patients [10]. In another series of three patients with meningeal carcinomatosis, symptoms of hydrocephalus were the presenting complaints with gait disturbance in all three, headaches in two of the patients, and altered mentation in one patient. Resolution of the symptoms of hydrocephalus occurred in all three patients with the insertion of a ventriculoperitoneal shunt. Although tumor responsiveness to radiation and/or chemotherapy as well as the burden of systemic disease ultimately influence survival in this patient population, placement of a ventriculoperitoneal shunt in patients who exhibit signs of hydrocephalus is beneficial, because it allows maintenance of a more meaningful quality of life. Lumboperitoneal shunts can be used in selective cases where CSF overproduction is a prominent feature.

Figure 21.4 A young patient presenting with signs of increased intracranial pressure underwent MRI that showed an intensely enhancing mass originating in the third ventricle causing obstructive hydrocephalus. Pathological examination of the surgical specimen revealed a choroid plexus papilloma.

Obstructive hydrocephalus secondary to a neoplasm is most commonly treated with surgical resection with or without external ventricular drainage, which is commonly temporary. Baroncini et al. described 284 adult and pediatric cases of tumors of the lateral ventricle in which two-thirds of the cases had some associated CSF disorder [11]. This group noted that neuropsychological deficits were the most frequent sequelae (22.8%) secondary to hydrocephalus [11]. Ventriculoperitoneal shunt implantation is the most common shunting procedure performed in patients with pediatric brain tumors, although endoscopic third ventriculostomy is often utilized in patients with tumors originating from the pineal region, thalamus, tectum, or pons.

Hydrocephalus can be a complication following radiation treatment secondary to radiation-induced edema. Following radiation, stiffening of the ventricles and effacement of the ventricular system can lead to increased intracranial pressure. More commonly this occurs in the setting of metastases to the posterior fossa with blockage of the fourth ventricle causing impaired CSF circulation. Hydrocephalus following radiation treatment can occur at any tumor location where the ventricular system has the potential to be obstructed secondary to mass effect from the underlying lesion or surrounding edema.

The association between spinal cord tumors and hydrocephalus was first described by Nonne in 1900 [12,13]. Kyrieleis described the first thoracolumbar tumor presenting with symptoms of hydrocephalus, headache, and papilledema, in 1931, and reported that removal of the tumor alleviated the symptoms [14,15]. With the development and implementation of CT and MR imaging the number of cases reported in the literature has grown to over 300. Mirone et al. contend that 1% of patients with intraspinal tumors will have some degree of hydrocephalus at initial presentation [15]. Rifkinson-Mann et al. described a series of 171 patients with intramedullary spinal cord tumors, in which 15% of the patients had symptomatic hydrocephalus. In this series, the authors also conclude that the patients with malignant intramedullary astrocytoma with associated hydrocephalus have a shorter survival time than patients with high grade lesions without hydrocephalus [16]. Astrocytomas and ependymomas are more frequently associated with hydrocephalus than other spinal tumor types and intramedullary tumors were associated with hydrocephalus almost 75% of the time[15]. Maroulis et al. analyzed the 269 patients with spinal cord tumors and hydrocephalus in the literature and concluded that in 47% of the cases, the two disease processes were diagnosed at the same time [17]. In this series, a history of either back pain, transient sphincter disturbance, or peripheral neurological signs raised suspicion of an underlying spinal lesion.

The pathophysiologic mechanism leading to hydrocephalus in patients harboring malignant intraspinal lesions is postulated to be secondary to the meningeal infiltration which increases resistance to CSF flow and absorption in the subarachnoid space. Several hypotheses have been suggested for the mechanism leading to hydrocephalus in patients with benign lesions: they range from alterations in the CSF pressure and flow from spinal obstruction, decreased CSF resorption around the spinal nerve sheaths, increased CSF viscosity secondary to increased protein content, increased deposition of fibrin, or outflow obstruction at the cervicomedullary junction [12]. While Rifkinson-Mann et al. concluded that rostral tumor cyst extension to the cervicomedullary junction was the predominant cause of the resultant hydrocephalus [16], Cinalli et al. contend that this most likely only represents a subset of tumor cases [12].

Surgical resection of the spinal lesion should be the first treatment when hydrocephalus and the intraspinal tumor are diagnosed at the same time, because removal of the lesion may resolve the hydrocephalus. Prior to surgical resection, a pan neuraxis MRI with contrast should be utilized to identify the extent of intracranial and spinal leptomeningeal seeding and other potential causes of hydrocephalus. In cases where leptomeningeal seeding is diffuse, hydrocephalus is likely to persist after tumor resection, making a shunting procedure necessary. This may be true in spite of the fact that certain authors contend that surgical trauma and/or the existence of a shunt could enhance tumor spread most likely due to changes in dissemination of neoplastic cells in the subarachnoid pathways and increase leptomeningeal seeding [15].

Hydrocephalus following subarachnoid hemorrhage (SAH)

Subarachnoid hemorrhage following aneurysmal rupture is a common disease process, first described by Bagley in 1928, that results in significant morbidity and mortality. Post-SAH hydrocephalus can be classified as either acute, occurring within 72 hours, subacute occurring over a few weeks, or chronic, occurring more than one month after the initial injury, resulting in permanent hydrocephalus often treated via CSF diversion. The development of hydrocephalus acutely can result in significant neurological disability, coma, and even death. Risk factors that predispose individuals to hydrocephalus include poor Hunt–Hess grade, intraventricular hemorrhage, history of hypertension, and aneurysms in the posterior circulation that can lead to obstruction of the fourth ventricle (Figure 21.5) [18–20].

Figure 21.5 This 71-year-old woman was emergently admitted to the hospital after she suddenly lost consciousness. CT showed extensive intraventricular and subarachnoid hemorrhage causing moderate to severe hydrocephalus.

Acute hydrocephalus following SAH is a common complication that is estimated to affect 20–30% of SAH patients [19,21,22]. The pathophysiological mechanism for the development of acute hydrocephalus is most often due to associated intraventricular hemorrhage which results in obstruction of CSF flow through the ventricular system and subarachnoid. In certain instances the increased subarachnoid blood and/or clot results in mass effect on the brain and ventricular system. The most common symptoms include headache, nausea, vomiting, impaired eye movements (particularly upward gaze), or impaired or decreased level of consciousness. The most significant symptom requiring intervention is decreased level of consciousness. Development of acute hydrocephalus is correlated with poor prognosis following subarachnoid hemorrhage [23]. In the acute setting, placement of an external ventricular drainage catheter is indicated. One study reported that approximately 29.6% of patients had acute hydrocephalus that resolved spontaneously within 48 hours of development, and 37.0% (10/27) of patients required intervention with external ventricular drainage due to either increased hydrocephalus or clinical deterioration [24].

Once the hydrocephalus moves past 72 hours, it enters the subacute or chronic phase. Under these circumstances patients generally undergo some type of shunting procedure. During surgery for aneurysmal subarachnoid hemorrhage, the lamina terminalis is typically opened to increase the operative exposure, but it also allows for increased drainage [25,26]. It has been suggested by Sindou et al. that fenestration of the lamina terminalis and Liliequist’s membrane improves overall prognosis in aneurysmal SAH patients [25,26]. Tomasello et al. demonstrated that lamina terminalis fenestration during aneurysm clipping in patients with subarachnoid hemorrhage resulted in a rate of 4.2% of postoperative hydrocephalus compared to the average of 20% [27]. The mechanism for decreased rates of hydrocephalus in these patients is thought to be related to the direct drainage of CSF from the lateral and third ventricles into the subarachnoid space, bypassing the cisterns of the base where scarring prompted by the blood might have occurred [28].

In patients requiring ventriculostomy for treatment of hydrocephalus, the criteria for weaning off an external ventricular drainage (EVD) system to ultimate removal versus placement of a shunt must also be considered. Klopfenstein et al. conducted a randomized controlled prospective study comparing gradual, multi-step EVD weaning versus rapid weaning [29]. This group demonstrated that a 96-hour trial, in which the external ventricular system was raised sequentially over every 24-hour period until the drain could be closed, provided no advantage in terms of preventing the need for permanent CSF diversion in comparison to a rapid wean, exemplified by immediate clamping of the EVD. The rate of shunting in both groups was ~60% [29].

Hydrocephalus following infection (post-infective)

Post-infective hydrocephalus is more commonly found in developing countries and has been reported to occur in 30–40% of hydrocephalus cases [30]. Post-infective hydrocephalus is commonly caused by either tuberculous or pyogenic meningitis [30].

In neonates, the most common organisms responsible for meningitis are E. coli and group B streptococci. The meningitis is usually acquired through maternal infection in neonates who have undergone a complicated labor or delivery with premature or prolonged rupture of membranes. More commonly the neonate suffers from generalized sepsis and the underlying meningitis is not recognized until later [31]. In preterm infants to children 3 months of age, group B streptococci, Staphylococcus species and Haemophilus influenzae are predominantly implicated, whereas in adolescents and young adults Neisseria meningitidis is the commonest organism responsible (Figure 21.6) [30].

Figure 21.6 This 27-year-old mentally retarded woman was born premature at 36 weeks. At 6 days after birth she developed Citrobacter meningitis and brain abscesses. She then developed hydrocephalus at 6 weeks and underwent shunt at about 2 months of age. She had a shunt revision in 1984 aged 6, another one in 1986 aged 8, one in 1996, and one in 1998. Since that surgery she had experienced intense dizziness. She had several shunt revisions between 2005 and 2006. MRI showed multiple porencephalic cysts in the bilateral frontal region, and left parietal region with ex-vacuo dilatation of the associated ventricles, and minimal gliotic change in the surrounding white matter without abnormal enhancement.

In pyogenic cases, the pathophysiologic mechanism for the resultant hydrocephalus is the increased cellularity and fibrotic adhesions that form on the arachnoid secondary to the inflammatory response of the offending organism. When meningitis occurs, the vessels become congested resulting in exudative material in the basal cisterns and ventricular system. As the fluid becomes more congested and turbid, the choroid and arachnoid tissue become covered in pus, which leads to leukocyte and plasma cell migration into the CSF circulation. In turn, the increased cellularity coupled with the fibrosis, adhesions, and septations that develop in the ventricles, cisterns, and arachnoid granulations impede CSF circulation and reabsorption causing hydrocephalus [30].

Toxoplasmosis is caused by the intracellular protozoan Toxoplasma gondii and most commonly occurs, in developed and developing countries alike, as a secondary infection in immunocompromised hosts, particularly those with HIV/AIDS. Congenital toxoplasmosis typically occurs in the infants of HIV/AIDS infected mothers [32]. T. gondii was described in 1908 in rodents and the first human case was later discovered in the retina of an infant who had hydrocephalus, seizures, and a unilateral ocular anomaly. On neuroimaging, single or multiple ring-enhancing mass lesions localized at the corticomedullary junction, in the white matter, or the basal ganglia are commonly seen, although cerebellar lesions have also been reported. Parenchymal involvement often causes extensive brain tissue necrosis and surrounding inflammation, which can potentially occlude the ventricular system, through mass effect on the cerebral aqueduct, foramen of Monro or fourth ventricle, or it can cause a ventriculitis. Similar to other disease processes, treatment should be directed at the underlying causative agent. In emergent situations where acute hydrocephalus is diagnosed, an external ventricular drainage device should be utilized to temporize the patient until anti-toxoplasma therapy can be initiated. For toxoplasma infection the most important method for treating and/or preventing the secondary effects of this disease is treating the immunocompromised state, particularly with HAART therapy in HIV/AIDS patients.

Ingestion of eggs from the tapeworm Taenia solium can lead to infection of the brain and covering meninges (neurocysticercosis). Once the oncospheres hatch in the intestine and penetrate the intestinal wall, the organism has an affinity for the central nervous system. Although epilepsy is the most common manifestation of neurocysticercosis, once the organism invades the ventricular system, acute hydrocephalus can occur. It is estimated that anywhere from 15% to 54% of cases present with the intraventricular form [33]. Neurocysticercosis most commonly affects the fourth ventricle (53%), followed by the third (27%) and then the lateral ventricle (11%) and cerebral aqueduct (9%). Once a cyst migrates to the fourth ventricle it can cause an obstructive hydrocephalus that can lead to rapid clinical deterioration. In one series, over 30% of patients presented with clinical deterioration and/or sudden death secondary to acute hydrocephalus. Scarring of the leptomeninges or arachnoiditis can lead to communicating hydrocephalus.

Intraventricular neurocysticercosis is diagnosed by the clinical presentation and imaging findings. Computed tomography (CT) is often used to initially diagnose the lesion, although its sensitivity is much lower given that the cyst contents and the CSF share the same density. As such, the cyst and the scolex may not be visible on CT. Cysts in the third ventricle often have the same appearance as a colloid cyst [34]. On MRI intraventricular cysts are identified 80% of the time with a spherical lesion seen on T1-weighted imaging with a hyperintense cyst wall and the scolex appearing as a mural nodule (Figure 21.7), whereas on T2-weighted imaging the cyst contents are isointense with a hyperintense scolex. Treatment for parasitic lesions is based on the clinical presentation and location of the cyst in the ventricular system. Emergent ventriculostomy should be the first treatment in cases of acute hydrocephalus as this procedure has the potential to be life-saving. Other interventions include ventriculoperitoneal shunt placement for obstructive hydrocephalus, and endoscopic or open surgical removal of the cyst. Although the cysts may be removed, ventriculoperitoneal shunting may be required afterwards [34]. In cases where shunting is required, the rate of revision can be as high as 30–67%, especially in cases complicated by ventriculitis [35,36]. Endoscopic treatment of ventricular neurocysticercosis has the advantage of allowing easy navigation through the ventricular system with minimal postoperative complications [37]. Several approaches and techniques have been described using endoscopic intervention for this disease process. Intraoperative rupture of the cyst may lead to ventriculitis necessitating continuous irrigation through the endoscope intraoperatively to help clear the contents and a potential shunting procedure postoperatively. Clinical outcomes from endoscopic treatment of neurocysticercosis are better than outcomes after open surgical procedures [33].

Figure 21.7 This 29-year-old woman from Bolivia developed headache, nausea and vomiting, and gait ataxia after a trip to her country. Sagittal T1-weighted image with gadolinium enhancement showed neurocysticercosis causing obstructive hydrocephalus.