Isolation of the fourth ventricle causing transtentorial herniation: neurosonographic findings in premature infants

Proposed radiological score for the evaluation of isolated fourth ventricle treated by endoscopic aqueductoplasty

PURPOSE

Evidence supporting the effectiveness of endoscopic aqueductoplasty (EA) for the treatment of isolated fourth ventricle (IFV) is limited to small surgical series of cases. Additionally, studies adopted different radiological outcome criteria, which makes it difficult to compare outcomes accurately. Thus, we aimed to develop a radiological score (RS) as an alternative assessment method for EA.

METHODS

The cases of 20 consecutive pediatric patients harboring IFV and treated by EA were retrospectively reviewed. Clinical data and pre- and 1-year postoperative brain images were analyzed. The RS was based on the enlargement of the fourth ventricle and deformation of the cerebellum and brainstem. After randomization, three experts, blinded to patient outcomes, analyzed the brain images and established a consensus for the values of the score. Outcomes were validated by comparing the maximum anteroposterior distance of the fourth ventricle using the RS, pediatric functional status score, and clinical symptoms.

RESULTS

The RS was strongly correlated with the anteroposterior distance of the fourth ventricle (Pearson's coefficient = 0.78), and the mean RS dropped from 6.15 to 3.90 (p < 0.001) 1 year after EA. Upward extension (p = 0.021) and brainstem deformation (p = 0.010) were the most significant improved features. There was agreement among RS and symptom improvement in 16 children (80%) and the pediatric functional status score in 14 children (70%).

CONCLUSION

In this study, the proposed radiological score proved to be an accurate tool for the evaluation of IFV treatment with EA.

Trapped fourth ventricle-treatment options and the role of open posterior fenestration in the surgical management

BACKGROUND

Trapped fourth ventricle (TFV) is a rare and difficult to treat condition. Most patients have a past inciting event (infection, IVH, trauma) and history of prior CSF diversion. The symptoms are due to the mass effect on brainstem and cerebellum. Rarely, TFV can also be associated with syrinx formation due to a dissociated craniospinal CSF flow near the fourth ventricle outlets. We present our experience and outcomes of open posterior fenestration in 11 cases, along with an overview of the surgical management of TFV.

METHODS

Between 2011 and 2018, 11 patients of TFV were operated by the posterior approach fenestration of the fourth ventricle outlets and arachnoid dissection. The clinical and radiological findings of the patients were retrieved from the hospital database. The surgical technique is described in detail. The patients' neurological status and imaging findings in the follow-up were recorded and compared.

RESULTS

The average age of the patients was 23.55 years. The most common presenting symptoms were headache (9/11) and gait imbalance (7), with TB meningitis being the commonest etiology. Ten patients had a history of prior CSF diversion with two presenting with shunt malfunction. Mean follow-up duration was 33.33 months. The improvement in neurological status was observed in 9/11 patients, 2 remained status quo. On follow-up imaging, 8/11 (72.72%) patients had a decrease in the size of TFV while syrinx improved in 3/5 (60%).

CONCLUSION

Multiple surgical approaches have been described for TFV. Endoscopic fourth ventriculostomy with aqueductoplasty is gaining popularity in the past two decades. However, an open posterior fenestration of the midline fourth ventricle outlet (magendieplasty) along with sharp arachnoid dissection (adhesiolysis) along the cerebello-medullary cisterns and paracervical gutters is relatively simple and provides physiological fourth ventricular CSF outflow. This is especially useful in TFV with syrinx as the craniospinal CSF circulation is established.

Neurosonography: Assessing the Premature Infant

Neurosonography has proven to be helpful in neonatal brain diagnosis. Premature infants are at great risk for intraventricular hemorrhage and periventricular leukomalacia, key abnormalities affecting developmental outcome. Here we discuss technique, anatomy, variants and key points for diagnosis.

Frequency and long-term follow-up of trapped fourth ventricle following neonatal posthemorrhagic hydrocephalus

OBJECTIVE Intraventricular hemorrhage (IVH) is a common complication of premature neonates with small birth weight, which often leads to hydrocephalus and treatment with ventriculoperitoneal (VP) shunting procedures. Trapped fourth ventricle (TFV) can be a devastating consequence of the subsequent occlusion of the cerebral aqueduct and foramina of Luschka and Magendie. METHODS The authors retrospectively reviewed 8 consecutive cases involving pediatric patients with TFV following VP shunting for IVH due to prematurity between 2003 and 2012. The patients ranged in gestational age from 23.0 to 32.0 weeks, with an average age at first shunting procedure of 6.1 weeks (range 3.1-12.7 weeks). Three patients were managed with surgery. Patients received long-term radiographic (mean 7.1 years; range 3.4-12.2 years) and clinical (mean 7.8 years; range 4.6-12.2 years) follow-up. RESULTS The frequency of TFV following VP shunting for neonatal posthemorrhagic hydrocephalus was found to be 15.4%. Three (37.5%) patients presented with symptoms of posterior fossa compression and were treated surgically. All of these patients showed signs of radiographic improvement with stable or improved clinical examinations during postoperative follow-up. Of the 5 patients treated conservatively, 80% experienced stable ventricular size and 1 patient experienced a slight increase (3 mm) on imaging. All of the nonsurgical patients showed stable to improved clinical examinations over the follow-up period. CONCLUSIONS The frequency of TFV among premature IVH patients is relatively high. Most patients with TFV are asymptomatic at presentation and can be managed without surgery. Symptomatic patients may be treated surgically for decompression of the fourth ventricle.

Disproportionately large communicating fourth ventricle resulting from adjustable valve shunt in an infant

Disproportionately large communicating fourth ventricle (DLCFV) is usually experienced in adults with no previous experience of shunting. We present a case of an infant with an enlarged fourth ventricle similar to isolated fourth ventricle (IFV) which appeared after shunting. The patient's brain stem symptoms and the abnormal appearance of the fourth ventricle were dramatically ameliorated simply by reducing the opening pressure of the adjustable valve of the ventriculo-peritoneal shunt. The present case suggests that in the present era, with adjustable or programmable valve shunt a common procedure, DLCFV may occur, at least temporarily, even in infants and even after shunting.

Management strategies for treatment of the trapped fourth ventricle

BACKGROUND

An isolated or trapped fourth ventricle (TFV) is an occasional, serious sequela of hemorrhagic, infectious, or inflammatory conditions of the central nervous system. The TFV usually occurs after successful shunting of the lateral ventricles. It may be heralded by delayed clinical deterioration after an initial period of symptomatic improvement. The typical clinical findings suggest an expanding posterior fossa mass lesion. Surgical treatments include CSF diversionary procedures as well as open and endoscopic approaches. Complications related to the treatment of the TFV are common and relate to catheter obstruction and cranial nerve or brainstem dysfunction.

METHODS

The author reviews the clinical features, pathophysiology, and available treatment options for the TFV, with special reference to complication avoidance and advances in ventriculoscopy and frameless stereotaxy.

CONCLUSIONS

Treatment of the TFV remains a formidable challenge. However, prompt recognition and intervention may aid in the preservation of life and neurological function.

Central nervous system candidiasis in the high-risk neonate

Central nervous system involvement in neonatal candidiasis is not rare, although possibly less frequent than in previous decades. In addition to increasing the potential for neurodevelopmental morbidity, this infection poses major challenges in establishing diagnosis and assuring adequate treatment. In the setting of candidemia or other severe invasive candida disease, suggestive imaging studies or inflammatory changes in cerebrospinal fluid should prompt careful consideration of central nervous system candidiasis even if culture of the fluid is negative. Although delivery of amphotericin to cerebrospinal fluid appears much better in premature infants than in older individuals, the availability of other agents with superior delivery to the central nervous system suggests that strong consideration be given to their use as alternative or adjunct therapy if central nervous system involvement appears likely. Careful surveillance for neurodevelopmental sequelae may permit early detection, timely rehabilitative intervention, and potentially better long-term functional outcomes.

Sonographic assessment of posthemorrhagic ventricular dilatation

Sonography plays a key role in the initial evaluation and monitoring of ventricular dilatation in the newborn. The use of supplemental imaging approaches by the mastoid fontanelle and foramen magnum can help identify the cause and location of obstruction. Duplex Doppler of intracranial vessels during anterior fontanelle compression is a useful indicator of altered cranial compliance in these infants. Additional views of the thoracolumbar spine can help identify which infants will likely benefit from lumbar puncture for therapy of progressive ventricular dilatation.

Rapidly progressive enlargement of the fourth ventricle in the preterm infant with post-haemorrhagic ventricular dilatation

Six preterm infants who developed disproportionate enlargement of the 4th ventricle during the neonatal period, associated with post-haemorrhagic ventricular dilatation (PHVD), before shunt placement are reported. Five of the six preterm infants developed cyanotic spells and/or bradycardias at the time of rapid enlargement of the 4th ventricle, suggestive of raised posterior fossa pressure, which resolved following insertion of and drainage from a subcutaneous reservoir. In one of the three survivors an isolated 4th ventricle was subsequently diagnosed later in infancy, requiring drainage. These data suggest that a combination of an enlarged 4th ventricle on ultrasound and cyanotic spells and/or bradycardias should lead to rapid release of raised pressure in the posterior fossa. Long-term follow-up of these children is necessary, as isolation of the 4th ventricle can subsequently develop.

Klebsiella oxytoca meningitis: frequent association with neurosurgical procedures

Klebsiella oxytoca meningitis is a rare condition. Nine patients were diagnosed between 1981 and 1993 at our institution. These accounted for 2.3% of 393 patients with blood and/or cerebrospinal fluid culture-proven bacterial meningitis. K. oxytoca was noted in both community-acquired meningitis and nosocomial meningitis. Eight of the nine cases were patients who had undergone neurosurgical procedures. Four were mixed bacterial meningitis. All K. oxytoca isolates were susceptible to third-generation cephalosporins and all but one to chloramphenicol. Antibiotic therapy was successful in eight patients but failed in one.

Transtentorial herniation of the fourth ventricle

Transtentorial herniation (TTH) of the fourth ventricle is the result of a progressive enlargement of an isolated fourth ventricle which herniates through the tentorial incisure into the middle cranial fossa. The characteristic CT-MR and neurosonographic findings are described.