Shunt malfunction presenting with symptomatic syringomyelia: Demonstrated on contrast ventriculogram.

Ventriculoperitoneal (VP) shunt malfunction commonly presents as raised intracranial pressure. Rarely, when the central canal of the spinal cord communicates with the 4(th) ventricle, shunt malfunction can present as an expanding syrinx. The diagnosis is often delayed, resulting in severe morbidity. Some of these patients undergo repeated syrinx surgeries without much benefits. We report a case of chronic tuberculous meningitis with shunt malfunction presenting as an expanding spinal canal syrinx and quadriparesis. Fourth ventricular communication with syrinx was demonstrated with the help of a contrast ventriculogram. After shunt revision, syrinx resolved completely and the patient made significant improvement in his neurological deficits. The present case illustrates that a historical and rarely used investigation like contrast ventriculogram aids in the diagnosis and management even in the current neurosurgical practice. All patients with late onset syrinx and a previous VP shunt need to be investigated for shunt malfunction before considering syrinx surgery. A simple shunt revision resolves the syrinx in such conditions and avoids more complex procedures like Foramen magnum decompression. Relevant literature has been reviewed; pathophysiology and management options have been discussed.

Introduction

Recurrent shunt malfunction is a known complication after ventriculoperitoneal (VP) shunt surgeries.[12] In chronic meningitis with hydrocephalus, VP shunts malfunction more frequently. Multiple shunt revisions are common resulting in significant morbidity.[2] Shunt malfunction commonly presents as recurrence of raised intracranial pressure (ICP).[1] We present an interesting case of chronic meningitis with shunt malfunction, presenting with expanding central canal syrinx and quadriparesis. This case was investigated with a contrast ventriculogram to demonstrate a communicating central canal syrinx. Later, he underwent a shunt revision and had a successful resolution of syrinx. The present case illustrates that a historical investigation like ventriculogram can still aid in diagnosis and management even in this modern era. Relevant English literature on shunt malfunction presenting with syringomyelia along with pathophysiology, its management and the role of contrast ventriculogram have been discussed.

Case Report

A 2-year-old toddler presented to us with chronic fever and raised ICP without any deficits in March 1998. He was evaluated with computed tomography (CT) of the head and was found to have mild communicating panventriculomegaly. His cerebrospinal fluid (CSF) on lumbar puncture showed lymphocytic pleocytosis. A provisional diagnosis of tubercular meningitis was made and he was started on empirical antitubercular therapy. His symptoms resolved then, but he presented back after 6 months with headache due to raised ICP. His repeat CT head revealed an increase in the size of ventricles for which he underwent a VP shunt. He had an episode of shunt malfunction after 3 months, and the VP shunt was revised. Nine months later he underwent laparoscopic repositioning of the abdominal end of the shunt due to loculated ascites (pseudocyst). He had multiple episodes of shunt malfunction in the next year, for which he underwent removal of peritoneal shunt and placement of a ventriculoatrial (VA) shunt. Subsequently he underwent revision of VA shunt too due to malfunction.

Six years later, he presented to our institute again with quadriparesis and truncal ataxia. On examination he was noted to have hypotonic quadriparesis, C5-D4 segmental dissociative sensory loss and absent reflexes. He was investigated with a craniospinal magnetic resonance imaging (MRI) [Figure 1a], which showed a cervicodorsal expanding syrinx and dilated 4th ventricle. Rest of the ventricular system was normal. Shunt tip was seen in situ. As he had no features of raised ICP, shunt malfunction was not thought of, and he underwent a syringopleural shunt. He was lost to follow-up only to present back after 5 years with recurrence of quadriparesis. He had scoliosis and hypotonic quadriparesis with a sensory dissociation. Craniospinal MRI [Figure 1b] showed reappearance of the syrinx with dilated 4th ventricle. The case was reviewed at this time, and the scans revealed that 4th ventricular size was seen progressively increasing, without a distinct communication between the central canal and 4th ventricle on comparison with previous MRI. Hence, a contrast ventriculogram [Figure 2] was performed through an external ventricular catheter to delineate the communication pattern. It demonstrated a mild ventriculomegaly with dilated 4th ventricle communicating with the dilated central canal of the spinal cord exceptionally well. Subsequently shunt malfunction was thought of, and he underwent removal of the VA shunt and placement of a fresh ventriculopleural shunt (as he had an abdominal pseudocyst). Lumbar puncture ruled out a reactivation of tuberculosis. The patient's weakness improved in the postoperative period, and he was doing well at the last follow-up (1-year). Postoperative MRI [Figure 3] showed significant resolution of syrinx and ventriculomegaly.

Figure 1

Preoperative magnetic resonance imaging of craniovertebral junction (a) done in 2004 showing - dilated fourth ventricle with syringomyelia for which he underwent a syringopleural shunt (b) done in 2009 showing - dilated fourth ventricle with reappearance of syrinx

Figure 2

Computed tomography contrast ventriculogram showing a fourth ventricular communication with the spinal canal (a) axial image at the level of the fourth ventricle with contrast (b) coronal image showing craniospinal canal communication (c) sagittal image showing contrast in the spinal canal

Figure 3

Follow-up magnetic resonance imaging with resolved syrinx (a) sagittal image with normal fourth ventricle and resolved syrinx (b) axial cuts showing normal fourth ventricle (c) Sagittal spine image with resolved syrinx

Discussion

Ventriculoperitoneal shunt malfunction is a commonly faced problem, and a number of cases undergo shunt revision.[12] Shunts in tubercular meningitis with hydrocephalus tend to malfunction more than others, especially if CSF proteins are high.[2] In the pediatric age group shunt malfunction commonly presents with headache, nausea, vomiting and drowsiness.[1] Lee et al. have reported on uncommon presenting features of shunt malfunction, and it includes seizures, vision loss, parkinsonian rigidity and syringomyelia (2 cases).[1] As such the causes of syringomyelia are many. This includes common congenital anomalies such as Chiari malformations, spinal cord injury, spinal arachnoiditis and sometimes tumors.[34] However, shunt malfunction presenting as spinal syrinx with quadriparesis is extremely rare.[567]

Our patient had tubercular meningitis with arachnoiditis which causes arachnoids’ scarring at the basal cisterns leading to communicating hydrocephalus. Probable 4th ventricular outlet obstruction at foramina of Luschka might have pushed the CSF into a patent central spinal canal (5th or terminal ventricle), which had been in communication with the 4th ventricle. Progressive dilation of the 4th ventricle and altered CSF flows across the foramen magnum would have caused the spinal syrinx to expand and propagate.[78]

If a shunt malfunctions, ventricular dilation is expected with symptoms of raised ICP. However, isolated enlargement of spinal central canal causing syrinx is also possible. The following mechanism may be proposed for this phenomenon. In long standing cases as in tubercular meningitis with arachnoiditis, the compliance of the ventricular system might have reduced, and it may not enlarge sufficiently. Furthermore, as spinal cords’ compliance is better-maintained, the central spinal canal may enlarge preferentially and cause the symptoms accordingly.

Misdiagnosis is common unless one is aware of this entity. PUBMED indexed English literature was reviewed to look for shunt malfunction presenting as syringomyelia. Eight case reports could be retrieved which have been tabulated [Table 1]. Milhorat et al. in 2003 have reported a patient of Chiari 1 malformation presenting with shunt malfunction causing acute quadriparesis and syringomyelia within 3 days. He promptly improved with shunt revision.[7] Beswick et al. in 2005 have described a similar case of postmeningitic hydrocephalus who presented 9 years after initial presentation with syringomyelia. He too had undergone multiple shunt revisions and posterior fossa decompression surgeries.[5] Lee et al. in their article on unique clinical presentation of paediatric shunt malfunction have reported that 2 (of 70 consecutive cases) had syringomyelia. Details were unavailable.[1] The review suggests that the primary pathology is mostly Chiari malformation or long standing meningitis like tubercular/posthemorrhagic meningitis. Syrinx can either be a de novo presentation or reappearance. Syrinx is a late complication of shunt-malfunction with an average duration of around 10 years (the range being 6 months to 19 years). Fourth ventricular outlet obstruction is seen in about 50% of the cases. Multiple shunt revisions and posterior fossa decompressions are also common before shunt malfunction is diagnosed. Furthermore, majority of them made clinical and radiological improvement following shunt revision.[567910111213]

Table 1

Cases of syringomyelia secondary to shunt malfunction

All the cases in this review should have had ventricle communicate with syringomyelia as the syrinx resolved after shunt surgery. Absence of ventricular communication with syrinx makes the posterior fossa decompression and other syrinx surgeries a necessity. The communication could be demonstrated in many, but not in all cases.[5610111213] When the communication is not clearly demonstrable, ventriculogram can be beneficial, as it confirms the anatomical communication. Contrast ventriculogram in syringohydromyelia was suggested by James et al. and has been extensively used in diagnosis and management in the past.[14] Furthermore, radioisotopes have been used for this purpose.[15]

Oi et al. have used contrast ventriculogram to correlate hydrocephalus, hydromyelia and isolated compartments. They have staged hydrocephalus as well as postshunt isolation of compartments. Among their 9 patients, 4 had holocord dilatation and hydrocephalus, and syringomyelia did not improve in 2 of them after a VP shunt.[16] Interestingly, the case reported by Muthukumar had anatomical communication (as per MRI), but shunt revision did not resolve the syrinx. Hence, their patient had to undergo posterior fossa decompression. This has been explained by the presence of an isolated compartment and hypothetical ventriculosyringeal valve at the proximal central canal.[1116] In the English literature, two other cases have been reported in which contrast ventriculogram was used in similar scenarios. Kudo et al. used it to confirm the communication between the 3rd and 4th ventricle in their case.[6] Matsumoto et al. in their case injected contrast through the shunt to see whether the ventricular or the peritoneal catheter got blocked.[13] In our case too, the contrast was injected through an external ventricular catheter to confirm the communication between the syrinx and 4th ventricle, as MRI was unclear. A number of these secondary syrinxes end up with repeat posterior fossa decompression surgery or syringosubarachnoid/pleural/atrial shunts, as in our case.[156] Though CSF flow studies may aid in the diagnoses, interpretation may be difficult at times. We believe that the diagnosis of communicating syringomyelia (hydromyelia) can be definitely established by demonstrating communication between the ventricles and the dilated central canal by positive contrast ventriculography.[15]

Conclusions

Patients with VP shunt with late onset syringomyelia need to be evaluated for shunt malfunction.

There seems to be a 4th ventricular outlet obstruction and its communication with a central canal which can sometimes be demonstrated by a contrast ventriculogram.

Recognizing this condition is very important as a simple shunt revision benefits the patient.