Early entrapment of fourth ventricle following Pseudomonas meningitis in extreme prematurity: Case report

Abbreviations

1 Case description

An 890 g female was born at 25 weeks’ gestation following maternal Pseudomonas aeruginosa chorioamnionitis secondary to preterm prolonged rupture of membranes (from 23 weeks). She required extensive respiratory and hemodynamic support since birth due to early fulminant Pseudomonas sepsis with meningitis (blood & cerebrospinal fluid (CSF) culture positive), complicated by disseminated intravascular coagulopathy and multi-organ failure.

Serial cranial ultrasonographies (CUS) during the first week of life showed the rapid progression from ventriculitis with ependymitis to widespread cerebral parenchymal ischemic infarcts, an extra-axial fluid collection with mass effect on the adjacent parenchyma and ventricular dilatation (Figs. 1, 2). Magnetic resonance imaging (MRI) of the brain was corroborative and an external ventricular drain (EVD) was inserted on day 24 of life to drain the subdural effusion. Brain MRI was repeated a week later to evaluate non-functioning of the EVD (Fig. 3). Proximal migration of the catheter with interval increase in the intra-ventricular echogenic debris was noted and the mal-positioned catheter was removed. Episodes of apnea, bradycardia, neck arching, and differential tone patterns between the extremities were evident over the following two weeks (34–48 days of life), raising concerns of elevated intracranial pressure. Serial CUS imaging revealed progressive panventricular dilatation and cystic lysis within the ischemic periventricular cortex. Of note, there was progressive and disproportionate dilatation of the fourth ventricle compared to the rest of the ventricular system with a classical key-hole configuration and significant effacement of the surrounding brainstem structures, strongly suggestive of a trapped fourth ventricle (TFV) with supratentorial herniation of the cerebellum (Fig. 4). The occipitofrontal circumference was below the 3rd centile & the Levene index below the 97th centile+4 mm during this period. Lumbar puncture yielded a dry tap. Brain MRI with CSF flow study was technically challenging in delineating the patency across the cerebral aqueduct. An interim ventricularaccess device was placed to facilitate urgent decompression of the posterior fossa and facilitate regular removal of CSF (Fig. 5).

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Fig.1

(A) Day 1 CUS coronal image at the level of posterior third ventricle shows echogenic and slightly thickened pial & ependymal linings (blank arrows), suggestive of meningitis (B) Day 7 CUS coronal image at the level of third ventricle shows large mixed echoic extra-axial/subdural collection (white arrows) with significant mass effect on underlying brain parenchyma with rightward midline shift (blank arrows).

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Fig.2

(A) Coronal and (B) Sagittal CUS on day 21 shows the progressive supra-tentorial ventricular dilatation and organisation within the left fronto-parietal collection.

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Fig.3

MRI Brain (C) Axial image demonstrates the large left fronto-parietal extra-axial collection with mass effect and midline shift. (D) Axial image shows marked cortical laminar necrosis of the cerebellum (E) Coronal T2 image shows the course of the external ventricular drain.

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Fig.4

(A) Coronal CUS image demonstrates markedly dilated and trapped fourth ventricle with “Key hole” configuration (Arrows with black borders). It appears disconnected from moderately dilated supra-tentorial ventricular system (blank arrows) and associated with significant mass effect.

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Fig.5

(A) Axial T2 W and (B) Coronal T2 W MRI Brain shows the trapped fourth ventricle (black arrows) & extra-axial/subdural collection in the left fronto-parietal convexity (white arrows). (C) Sagittal T2 W MRI Brain with markedly dilated fourth ventricle that appears to be isolated from moderately dilated supra-tentorial ventricular system superiorly (black arrows) and 4th ventricular exit foramina infero-laterally; with mass effect on posterior fossa structures & effacement of CSF spaces.

At term equivalent gestational age, an attempt to direct micro-surgical fourth ventricle outlet fenestration via sub occipital craniotomy had to be abandoned due to profuse bleeding from the thickened meninges and dural venous sinuses and a fourth ventriculoperitoneal shunt was placed. The infant had microcephaly and a poor neurological profile on the Hammersmith Infant Neurological Examination at discharge.

Multiple hospitalizations were needed over the first two years of life for concerns of seizures, lethargy and poor feeding. Neurosurgical interventions included a supratentorial VP shunt at four months, a neuro-endoscopic fenestration of the porencephalic cyst at 9 months and revisions of prior VP shunts thereafter (Fig. 6). At the corrected age of two years, the child had severe spastic quadriplegic cerebral palsy, global developmental delay, refractory myoclonic seizures, bilateral blindness secondary to Pseudomonas keratitis, and severe retinopathy of prematurity.

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Fig.6

MRI Brain at 6 months of age (A, B) T2 axial images shows complex hydrocephalus (white arrows) with tip of the 4th ventricular shunt insitu (black arrows) and changes of retinal detachment & ocular collections in eye globes (blank arrow heads in image B). (C & E) Sagittal T1, T2 images of the complex hydrocephalus with syringo-hydromyelia of the included cervico-dorsal spinal cord (Blank arrows in image E). (D) Coronal FLAIR image shows marked encephalomalacia and porencephalic cyst in the left parietal lobe (blank arrows).

Pseudomonas aeruginosa, a highly adaptable gram negative bacillus, is a nosocomial pathogen predominantly associated with late onset neonatal sepsis in developing countries and occasionally encountered in the developed world [1]. Prolonged antibiotic treatment in pregnancies with preterm premature rupture of membranes has led to the increased risk of early onset sepsis by Pseudomonas among the extremely low gestational age newborns (ELGAN) [2]. Pseudomonas aeruginosa can be highly virulent among this immune-compromised group and is associated with a high mortality rate (>50%) [1]. TFV, as a late sequel of neonatal posthaemorrhagic hydrocephalus following VP shunting, has been well reported. Pomeraniec [3] reported its frequency as 15.4% over a 10-year period and the mean age at diagnosis was 20 months. Gram negative bacterial meningitis (E. coli) has been reported as a frequent cause of post inflammatory cystic hydrocephalus with compartmentalization of the ventricular system [4]. Inflamed ependymal surfaces result in obstructive adhesions across the CSF pathways and lead to aqueductal stenosis and obstruction of the foramina of Luschka and Magendie. TFV secondary to fulminant Pseudomonas meningitis in surviving ELGANs are very rare. Another distinguishing feature of our case is the early age at presentation (6 weeks of life) prior to VP shunt.

Sequential CUS imaging, through the anterior fontanel is the primary imaging modality to depict the rapid progression of fulminant bacterial meningitis and its complications, including extra-axial fluid collections, disproportionate dilatation of the ventricular system (eg.TFV), and the extent of parenchymal infarcts [5]. Routine posterior fossa imaging via additional acoustic windows (mastoid and trans-temporal) can provide vital evidence of cerebellar injury and early clues to the emergence of TFV [6]. The entire ventricular system and patency of the cerebral aqueduct can be visualized by axial images through the mastoid fontanel. The signs of brain stem compression due to TFV can be vague and subtle in neonates viz; opisthotonic posture, respiratory instability, bradycardia, vomiting, and lethargy, which may be attributed to the relatively common issues of prematurity such as gastroesophageal reflux, apnea of prematurity etc. Heightened clinical suspicion with appropriate radiological correlation is hence critical to identify a symptomatic TFV in preterm infants.

Conventional clinical parameters used to guide surgical intervention (increasing occipitofrontal circumference > 7 mm/ week, tense fontanels, widening sutures > 5 mm, Levene index > 97th centile + 4 mm) appear quite late in the clinical course of hydrocephalus regardless of the anatomical details. Several neurophysiological assessment tools have been proved to identify early reversible cerebral injury secondary to post-hemorrhagic hydrocephalus (PHH). In the Klebermass study [7] on 17 preterm infants with PHH, worsening patterns in flash visual evoked potential (fVEP) latencies and amplitude-integrated EEG (aEEG) were evident earlier than CUS features and found to be reversible within a week of CSF drainage. Prolongation of fVEP latencies was more consistent than suppression of the background pattern of aEEG to indicate early reversible cerebral dysfunction [8].

The appropriate time and choice of surgical intervention varies widely and is determined by the underlying etiopathogenesis and regional expertise. Treatment modalities are diverse and range from open surgery to CSF diversions and endoscopic procedures (aqueductoplasty/stenting) [9, 10]. Though there is no consensus, neuro-endoscopic aqueductoplasty or interventriculostomy with fourth ventricular stenting is recommended as a minimally invasive and effective first line of management [3, 11]. Direct decompression and insertion of a ventricular access device (VAD) in the fourth ventricle still has a role in the preterm patients to allow for adequate weight gain or clearance of the proteinaceous debris in the ventricular system [12]. However, a definitive fourth ventricle shunt via the standard suboccipital approach or the alternative trans-tentorial approach is inevitable.

3 Conclusion

This case is reported for the early entrapment of fourth ventricle consequent to a relatively rare infectious etiology and the extensive brain injury that followed early onset Pseudomonas septicemia in a surviving ELGAN. Prompt identification of TFV in prematurity requires heightened clinical suspicion. Using additional acoustic windows during sequential CUS imaging in high risk infants may provide early valuable information of the posterior fossa structures and the ventricular system. Neurophysiological assessment tools and minimally invasive endoscopic surgeries are recommended to optimize management decisions and preserve neurological function.

Disclosure statements

All information that could reveal the identity of our patient has been removed and written informed consent was provided by the parents.