Endoscopic Third Ventriculostomy in Post-Tubercular Meningitic Hydrocephalus

Sir,

It is with interest that we note the paper by Singh et al. reporting on endoscopic third ventriculostomy (ETV) in post-tubercular meningitic hydrocephalus [1]. They report on a prospective study of 35 patients, 54.3 % of whom are described as having obstructive hydrocephalus and 45.7 % with communicating hydrocephalus. These are defined by the authors using certain criteria. The discrepancy between large supratentorial ventricles and a smaller fourth ventricle is used to identify aqueduct stenosis and a large fourth ventricle identifies obstruction of the foramina of Luschka and Magendie. However, we have had hydrocephalic patients with a relatively small fourth ventricle on computed tomography (CT) scans in whom magnetic resonance imaging (MRI) revealed patency of the aqueduct (Fig. [1]). Also, we have investigated patients with a dilated fourth ventricle with air studies and found no obstruction to the outlet foramina.

Fig. 1 A CT scan showing triventricular hydrocephalus. B Sagittal MRI scan showing the same patient with a patent cerebral aqueduct. ETV was attempted because of shunt dysfunction but also failed.

Communicating hydrocephalus is defined in this paper by the presence of cerebrospinal fluid (CSF) in the subarachnoid spaces. However, Bruwer et al. [2] convincingly demonstrated that CT findings are not reliable in the prediction of the level of block in tuberculous hydrocephalus. This was supported by a report from our institution [3]. CSF in the subarachnoid space is not a reliable predictor of communicating hydrocephalus.

In a separate report by Lamprecht et al. the incidence of non-communicating hydrocephalus was 17 % [4]. This is in keeping with the older reports of this condition that demonstrate the CSF block to be predominantly at the level of the basal cisterns. The series by Lamprecht et al. is of particular interest because patients with communicating hydrocephalus were treated medically in the first instance with a combination of anti-tuberculous medication, steroids, acetazolamide and furosemide, with regular pressure monitoring. Medical treatment of the hydrocephalus was successful in 75 % of the cases, i. e., these patients required no surgical treatment for hydrocephalus. Response can be assessed by the improvement in the appearance of the CT scan and confirmed by lumbar pressure monitoring, an example of which is shown in Fig. [2].

Fig. 2 A CT scan appearance before (left) and after (right) one month of medical treatment as described. B The accompanying decrease in pressure on lumbar pressure monitoring before (above) and one month after (below) commencement of medical treatment.

Visudiphan et al. [5] also confirm a very high rate of success with a medical strategy that avoids surgical treatment. This is worth keeping in mind when one considers the ETV success rate reported in this paper of 84.2 % for obstructed hydrocephalus and 68.7 % for communicating hydrocephalus. From the authors' description we are unsure that there was the same targeted approach to the medical treatment of hydrocephalus in the early and intermediate group.

As we have added to our original experience with endoscopy in tuberculous hydrocephalus we have progressively refined our approach. We agree with the authors that TBM is a challenge for the endoscopist because of the technical difficulty, which we initially reported [6]. This is precisely why we believe that a more selective approach should be taken to the management of these patients. We do not believe that ETV is appropriate if one can demonstrate with the use of air encephalography or MRI scans an unimpeded passage of CSF flow through the ventricle system and to the basal cisterns. Modified air encephalography can be performed safely; however a strict protocol must be adhered to [3]. According to our thinking this is preferable to performing an unnecessary endoscopic procedure, particularly in a group of patients who experience such a high rate of success with adequate medical treatment alone.

References

• 1 Singh D, Sachdev V, Singh A K, Sinha S. Endoscopic third ventriculostomy in post-tubercular meningitic hydrocephalus: a preliminary report.  Minim Invas Neurosurg. 2005;  48 47-52
• 2 Bruwer G E, Westhuizen S Van Der, Lombard C J, Schoeman J F. Can CT predict the level of CSF block in tuberculous hydrocephalus.  Childs Nerv Syst. 2004;  20 183-187
• 3 Figaji A A, Fieggen A G, Peter J C. Air encephalography for hydrocephalus in the era of neuroendoscopy.  Childs Nerv Syst. 2005;  21 559-565
• 4 Lamprecht D, Schoeman J, Donald P, Hartzenberg H. Ventriculoperitoneal shunting in childhood tuberculous meningitis.  Brit J Neurosurg. 2001;  15 119-125
• 5 Visudhiphan P, Chiemchanya S. Hydrocephalus in tuberculous meningitis in children: Treatment with acetazolamide and repeated lumbar puncture.  J Pediatr. 1979;  95 657-660
• 6 Figaji A A, Fieggen A G, Peter J C. Endoscopic third ventriculostomy in tuberculous meningitis.  Childs Nerv Syst. 2003;  19 217-225