Trapped or isolated fourth ventricle (IFV) is a relatively rare but critical neurosurgical condition, mostly affecting pediatric patients with a history of supratentorial shunting for hydrocephalus, intraventricular hemorrhage (IVH), as well as central nervous system inflammation, infection, or brain tumors.1 The direct cause of IFV is obstruction of the FV inlets (the aqueduct of Sylvius) and outlets (the foramina of Magendie and Luschka), usually due to adhesions or overdrainage following shunting. This leads to an accumulation of cerebrospinal fluid in the FV, which dilates and compresses the cerebellum and brainstem, with potentially fatal consequences.2

A previously healthy male newborn, delivered naturally at term, was awake for feeding on day 13 of his life, when he suddenly developed irregular breathing, generalized hypotonia, pallor, and unresponsiveness, progressing to respiratory arrest at home. Cardiopulmonary resuscitation was initiated, and the infant was admitted to a neonatal pathology unit in a critical condition. On admission, he was apneic, cyanotic, and had bilaterally constricted pupils with minimal reaction to light. Mechanical ventilation and analgosedation were initiated. Oxygen saturation was 98% with the fraction of inspired oxygen at 0.2 l/kg/min, blood pressure of 92/72 mm Hg, and heart rate of 200 bpm. Physical examination showed a tense anterior fontanelle, positive setting-sun sign, globally decreased muscle tone, and absent reflexes. Laboratory test results yielded mixed acidosis with pH at 7.03 (reference range [RR], 7.35–7.46) and hypercapnia, with partial pressure of carbon dioxide of 65 mm Hg (RR, 31–48 mm Hg). Additional abnormalities included hyperlactatemia with the lactate level of 7.2 mmol/l (RR, 0.3–0.8 mmol/l), hyperglycemia with glucose concentration at 28.9 mmol/l (RR, 3.3–5.6 mmol/l), leukocytosis (leucocytes, 19.09 × 103/μl; RR, 8.04–15.4 × 103/μl) with neutrophilia (neutrophils, 13 × 103/μl; RR, 1.6–6.1 × 103/μl), thrombocytosis (thrombocytes, 552 × 103/μl; RR, 150–350 × 103/μl), mild hyponatremia with the level of sodium at 133 mmol/l (RR, 134–144 mmol/l), and unconjugated bilirubin level of 42.7 μmol/l (RR, 3–22 μmol/l).Lung auscultation identified bilateral rhonchi and crackles. Blood cultures were negative. The results of extended coagulation studies and tandem mass spectrometry newborn screening were unremarkable.

Immediate cranial ultrasound, followed by confirmatory computed tomography (CT) of the head showed massive bilateral grade III/IV IVH with a blood-filled FV compressing the posterior fossa structures (Figure 1A–1C). CT was performed instead of magnetic resonance imaging (MRI) due to the life-threatening clinical condition requiring immediate assessment, as well as to confirm the extent of intraventricular hemorrhage.

Figure 1. Imaging findings in a patient with intraventricular hemorrhage leading to an isolated fourth ventricle; A – posterior cranial fossa ultrasound showing a blood-filled fourth ventricle (arrow); B – axial computed tomography (CT) image showing enlarged, blood-filled lateral (white arrows) and third (black arrow) ventricles with cerebral edema; C – sagittal CT image showing blood in the third (black arrow) and fourth (white arrow) ventricles and basal cisterns (green arrows) with cisterna magna (blue arrow); D – axial CT scan showing regression of the supratentorial intraventricular hemorrhage and a right frontal shunt tip in the third ventricle (arrow); E – axial T2-weighted magnetic resonance imaging (MRI) scan showing narrow, asymmetric supratentorial ventricles (arrows); F – sagittal T2-weighted MRI image showing aqueductal obstruction (white arrow) and an enlarged fourth ventricle with an adhesion (black arrow), compressing the brainstem (white star) and cerebellum (blue star); G – axial T2-weightd MRI image visualizing supratentorial ventricle improvement after overdrainage (arrows); H – sagittal T2-weighted MRI image showing reduced fourth ventricle dilation (black arrow) and posterior fossa compression with brainstem (white arrow)

Consequently, urgent external ventricular drainage was performed on day 14 of the patient’s life. CT angiography did not demonstrate any vascular malformations, and cardiological evaluation was normal. Mechanical ventilation continued until day 10 of hospitalization, and full enteral feeding tolerance was achieved by day 9 after parenteral and nasogastric feeding. Serial imaging showed regular regression of hemorrhagic lesions and a slight reduction of ventricular dilatation. Thirty-one days after admission, the external ventricular drain was converted to a ventriculoperitoneal shunt (Figure 1D), after which the patient remained in a good and stable clinical condition.

One year later, control MRI showed a narrow supratentorial ventricular system (Figure 1E) and a relatively dilated FV with aqueductal obstruction, compressing the brainstem and cerebellum (Figure 1F). The patient exhibited convergent strabismus, increased upper limb tone, and decreased, lower limb and axial tone. IFV was diagnosed and neurosurgeons performed suboccipital craniotomy with C1 laminectomy, open fenestration of the FV to the cisterna magna, endoscopic aqueductoplasty via an inferior approach, and attempted recanalization of the foramina of Luschka and Magendie. The perioperative course was uneventful, and follow-up MRI showed reduced FV dilation (Figure 1G and 1H). Clinically, convergent strabismus and psychomotor delay persisted, but no further neurological deterioration was observed.

Possible causes of IVH include hemorrhagic stroke, prematurity, coagulopathy, genetic disorders, infection, trauma, tumors, and vascular malformations.3 In this case, most causes were excluded, suggesting idiopathic IVH or the need for further advanced diagnostics. Despite the initially critical presentation, rapid intervention preserved the patient’s vital and neurological functions.

IFV may present as delayed clinical and radiological deterioration after an initial period of symptomatic improvement following supratentorial shunting. Prompt recognition and timely intervention are essential to prevent cerebellar / brainstem syndrome. Although IFV management remains challenging, several treatment options are available, including endoscopic techniques, microsurgery, or shunting, and they may be combined.1,2 In this patient, the goal of the combined surgical approach was to maximize cerebrospinal fluid outflow from the FV while avoiding implantation of an additional foreign body, as required in FV shunting, thereby reducing infection risk.4

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How to cite Kasza G, Kwiatkowki S, Klasa Ł, Milczarek O. Excessive intraventricular hemorrhage resulting in an isolated fourth ventricle in an otherwise healthy full-term infant. Prz Lek Jagiellonian Med Rev. 2026; 78: 20041. doi:10.20452/jmr.2026.20041