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|LETTER TO EDITOR
|Year : 2013 | Volume
| Issue : 1 | Page : 93-94
Unusual complication of a shunted intracranial arachnoid cyst mimicking cyst recurrence
Sumit Thakar, Sunil Valentine Furtado, Alangar Hegde
Department of Neurosurgery, Sri Sathya Sai Institute of Higher Medical Sciences, Whitefield, Bangalore - 560 066, India
|Date of Submission||30-Nov-2012|
|Date of Decision||30-Dec-2012|
|Date of Acceptance||20-Jan-2013|
|Date of Web Publication||4-Mar-2013|
Department of Neurosurgery, Sri Sathya Sai Institute of Higher Medical Sciences, Whitefield, Bangalore - 560 066
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Thakar S, Furtado SV, Hegde A. Unusual complication of a shunted intracranial arachnoid cyst mimicking cyst recurrence
. Neurol India 2013;61:93-4
Although infection is the second most common complication of an intracranial-peritoneal shunt, the formation of a shunt-related intracranial abscess is rare. ,,,,,,, We describe a patient with an intracranial arachnoid cyst that presented with a delayed abscess mimicking cyst recurrence after a cysto-peritoneal shunt.
A 32-year-old man presented with history of headache, vomiting, and rapidly progressive weakness of the right-sided limbs of duration of 2 weeks. He was diagnosed to have an intracranial arachnoid cyst 6 years back and had undergone a cysto-peritoneal shunt for the same. Positive findings on neurological examination included papilledema and right-sided hemiparesis (grade 3-4 power). There were no signs of meningeal irritation. Review of his old magnetic resonance imaging (MRI) revealed a 5 × 5.5 × 6 cm, cystic, non-enhancing lesion of cerebrospinal fluid intensity in the interhemispheric bifrontal region [Figure 1]a-c. There was evident mass effect on the surrounding brain. A follow-up computed tomography (CT) scan done a month prior to the current admission showed a well-decompressed cyst [Figure 1]d. Non-contrast MRI at admission showed a 4 × 4.5 × 5 cm sized, left frontal lesion [Figure 2]a and b of intensities similar to those of the previous lesion. There was significant mass effect with midline shift to the right. The initial radiological impression was that of shunt dysfunction with cyst recurrence. However, features like the rapid-onset focal neurological deficit and the perilesional edema seen on the T2-weighted sequences [Figure 2]b prompted further evaluation. Contrast MRI revealed peripheral enhancement and diffusion-weighted imaging showed restricted diffusion [Figure 2]c and d. Based on these additional pointers, the diagnosis of a shunt-related abscess was made after ruling out other sources of infection. The patient underwent burr-hole aspiration of the abscess and removal of the entire shunt system. The pus culture remained sterile. He was empirically treated with a course of ceftriaxone, amikacin, and metronidazole for 2 weeks, followed by oral cefuroxime for a month, with good results [Figure 2]e. He has been advised regular follow-up to check for recurrence of the arachnoid cyst.
|Figure 1: (a) Preoperative post-contrast T1-weighted image and (b) T2-weighted image, axial sections, showing a 5 × 5.5 × 6 cm cystic lesion of cerebrospinal fluid intensity in the interhemispheric, bifrontal region with mass effect. (c) Diffusion-weighted sequence showing absence of restriction in the lesion. (d) Follow-up CT brain showing the tip of the cysto-peritoneal shunt in a well-decompressed cyst|
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|Figure 2: (a) Plain T1 - weighted and (b) T2 - weighted images, axial sections, showing a 4 × 4.5 × 5 cm sized, left frontal lesion of cerebrospinal fluid intensity. There is perilesional edema with mass effect and midline shift to the right. (c) Post-contrast T1-weighted image, axial section, showing intense peripheral enhancement. (d) Restriction of diffusion noted on diffusion-weighted sequences. (e) Postoperative CT brain with contrast showing resolution of the abscess. Some residual edema is noted|
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Despite the introduction of modern shunt systems and new antibiotics, infection after an intracranial-peritoneal shunt still remains a serious complication. This commonly presents as shunt infection or dysfunction, meningitis, or ventriculitis. The rare, shunt-related abscesses have been postulated to be related to ascending gram-negative enteric organisms from sources of abdominal sepsis in most cases.  There have also been anecdotal reports of abscesses forming in relation to retained ventricular catheters in non-functioning or disconnected shunt systems, ,, implying that the source of infection in these cases may have been colonized bacteria on the external surface of the ventricular catheter during initial shunt insertion. This has led to the suggestion that retained catheters in non-functioning shunt systems ought to be removed.  Because of the associated risk of bleeding, care needs to be exercised during shunt removal in longstanding cases, and this may necessitate endoscopic assistance. The abscess may be excised or drained, and the patient is then managed with a course of culture-specific or empirical antibiotics, like for any other intracerebral abscess.
In our case, the abscess had developed as a delayed complication of a functioning cysto-peritoneal shunt in the absence of any abdominal sepsis. The diagnosis was almost missed at presentation when only a plain MRI was done. The enhancing pattern and restricted diffusion clinched the diagnosis. A radiological differential diagnosis of this presentation would have been an infected epidermoid if the previous history was to be ignored.
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[Figure 1], [Figure 2]