Ventriculo-peritoneal shunt: A rare cause of basal ganglia and thalamic abscess.

We report an 18-month-old female child with ventriculo-peritoneal shunt related thalamic abscess treated with stereotactic aspiration. Deep seated abscesses are complex due to difficult access and are associated with an increased risk of intra-ventricular rupture as well as antibiotic resistance, a fact which justifies a more aggressive and immediate neurosurgical management.

Introduction

Brain abscess though less common, continues to constitute one of the most important neurological emergencies with potential poor outcome. Thalamic and basal ganglia abscesses are much rarer than abscesses in other locations of the brain. Only a few cases of such inflammatory lesions have been reported [Table 1]. We report a rare case of basal ganglia and thalamic abscess as a complication of ventriculo-peritoneal (VP) shunt.

Table 1

Pediatric basal ganglia and thalamic abscess reported cases

Case Report

An 18-month-old female child presented with fever, vomiting off and on for 2½ months and altered sensorium and seizure for 1 day at an outlying hospital.

Child was operated at 25 days of life for cervical meningomyelocele and VP shunt was placed for hydrocephalus. Shunt revision was carried out at 1½ month of age for oozing from surgical site. At 6-month of age, VP shunt was seen protruding through anus, for which distal end of shunt was shortened surgically and shunt left in situ at the outlying hospital. No shunt revision was performed. Child remained well for next 1 year. At 18-month of age, child was referred to us with altered sensorium and Glasgow Coma Score of 8/15. Magnetic resonance imaging (MRI) revealed multiple abscesses in the left basal ganglia and one in thalamus which measured approximately 25 mm × 24 mm with midline shift of 11 mm [Figure 1] and shunt was transversing through the trigone, quadrigeminal area into the thalamic area on the contra-lateral side. Investigation revealed high total leukocyte count (25700/mm3) with thrombocytosis (469 × 105), prothrombin time/international normalized ratio-20.1/1.99, Na+-123 mEq/L. Child was managed with mechanical ventilation, 3% saline, intravenous Meropenem (120 mg/kg/day q 8 h) and Vancomycin (60 mg/kg/day q 6 h) empirically. Hyponatremia was corrected gradually over next 48 h. VP shunt was removed and external ventricular drain (EVD) was placed in right ventricle for immediate decompression followed by stereotactic aspiration of abscess. Morganella morgagni, Klebsiella pneumonia, and Enterococcus faecalis were isolated from the pus and M. morgagni was isolated from blood. As per the sensitivity intravenous colistin (1.2 lakh IU/kg/day q 8 h) was added. EVD got dislocated and omaya reservoir was placed. Intravenous antibiotics were given for a total of 6 weeks and subsequently patient underwent VP shunt revision.

Figure 1

Magnetic resonance imaging brain showing abscess in left thalamic and basal ganglia (see arrow) with midline shift to right

Discussion

Early diagnosis and successful treatment of brain abscess still remains a clinical challenge. Thalamic and basal ganglia abscesses are relatively rare, the reported incidence varies from 1.3-6% of brain abscesses.[1] Thalamic abscesses are metastatic lesions of hematogenous origin, mostly from congenital heart disease, intra-thoracic sepsis, abdominal sepsis, cryptogenic and of local origin, from dental caries, otitis media, and sinusitis.[123] Immuno-compromised state is one of the predisposing factors; however, in many cases source of sepsis or predisposing factor could not be determined.[24] In our case, there was a retrograde spread of shunt infection from the colonic bacteria as the shunt that was protruding through the anus was only repositioned and not completely replaced. This is the most likely cause of thalamic abscess in our patient. Most patients present with fever with leukocytosis, signs of raised intracranial pressure such as headache, altered sensorium, and hemiparesis.

Computed tomography (CT) and MRI have facilitated the rapid identification of thalamic and basal ganglia abscesses. Differential diagnosis includes fungal, nocardial or tubercular abscesses, neurocysticercosis, toxoplasmosis, glioblastoma, metastasis, infarction, and resolving hematoma.[125] The diagnosis can be difficult, particularly in the absence of fever and serological signs of infection. A tissue diagnosis should be attempted using stereotactic procedure if available.

The best surgical management of a thalamic abscess remains controversial. Treatment options include stereotactic aspiration with or without continuous drainage,[467] free hand aspirations through a burr hole,[3] stereo-endoscopic aspiration,[89] ultrasound guided aspiration, surgical trans-ventricular approach, and medical management. Stereotactic aspiration remains the preferred treatment as it drains the contents of the abscess, reduces mass effect, and confirms diagnosis.[46] It is minimally invasive; carries less morbidity, mortality, and can be performed on compromised patients under local anesthesia.[6] Reported incidence of complications with stereotactic surgery is 7.2% and incidence of symptomatic hemorrhage ranges from 0-5.3%.[8] Since the procedure is blind, there are chances of incomplete evacuation with recurrence of abscess and fulminant ventriculitis by intra-ventricular leakage. After stereotactic aspiration or drainage, VP shunt may be required in 50% of the cases.[3]

Evacuation of brain abscess by a stereotactic endoscope has been reported by Wan and Jiang[8] The endoscopic aspiration with antibiotic irrigation of thalamic abscess was successfully reported by Gajdhar and Yadav[9] Advantage of this technique was aspiration of abscess under direct visualization with dissolution of loculi, direct assessment of completeness of aspiration and lesser chances of complications like hemorrhage.

The ability to monitor the drainage by using near-real-time imaging information is exceptional with MRI.[10] Multiplanar capabilities, high spatial resolution, excellent soft-tissue contrast and the absence of ionizing radiation with MRI makes it a more attractive alternative; however, high cost may limit the availability. In our case, due to non-availability of real-time MRI at our institution, CT guided stereotactic evacuation of the abscess was performed with good results.

Conclusion

Ascending infection with gram negative enteric organisms in central nervous system is a known complication of VP shunt, may rarely cause abscess in thalamus and basal ganglia requiring neuro-intensive care, early drainage, appropriate antibiotics, and stereotactic neurosurgical intervention.