Response to Letter Endoscopic Third Ventriculostomy in Post-Tubercular Meningitic Hydrocephalus

Sir,

This is in relation to the letter and the comments expressed by Figaji et al. [1] to our article on the ETV in tubercular hydrocephalus [2].

At the outset we express our sincere gratitude and thanks to the authors for liking the article and for expressing keen interest in the subject. We also comprehend that both TBM and hydrocephalus are topics of great debate, however, we would like to attempt to clarify some of the doubts raised by the authors from our experience.

We fully agree with the authors that it is not always possible to accurately classify hydrocephalus into communicating and non-communicating forms based upon a CT scan alone. We feel the same for MRI even though it is superior to CT in demonstrating aqueduct anatomy and the subarachnoid spaces.

Regarding an air encephalogram (CT or otherwise) as an additional test to classify hydrocephalus into two groups, i.e., communicating and non-communicating, we are of the opinion that this may not be a significant advantage. Being lighter in density air in any case is likely to sneak into the ventricles or subarachnoid spaces from small creases/holes within the exudates or blocks. Hence, most authors have found a high incidence of communicating hydrocephalus in TBM on AEG.

CSF, on the other hand, will not pass from such creases as air would do. This is similar to a block drain from which air can purge through but retains the water. Moreover, CSF may not be adequately flowing in volume from such spaces, resulting in functional obstruction. Therefore, we feel that AEG cannot be considered as the gold standard for classifying hydrocephalus as well as for deciding upon a method of treatment.

Hence the criteria followed by us were reasonable indirect clues in the CT scan to classify hydrocephalus into two groups.

It is further submitted that the division of hydrocephalus into communicating and non-communicating is an oversimplification of the age-old understanding. The present concept of hydrocephalus is based upon pulsatilc flow of CSF. It is now believed that acute hydrocephalus is caused by obstruction to the CSF flow. Chronic hydrocephalus, as often seen in TBM, is not due to malabsorption of CSF but is due to increased pulse pressure in the brain [3]. ETV possibly changes the pulsatile pressure and hence produces the desired benefits.

In our article ETV in TBM was done in those who failed to respond to medical treatment. However, we have observed over the years that overjudicious medical treatment delays and denies the merit of surgical procedures. Medical or surgical treatment in our place is primarily determined by the clinical status of the patient (stage of TBM) and not by the phase of TBM, i.e., early, intermediate or late (duration of disease).

A patient who is decerebrating or is in a severe neurological status or altered sensorium is best treated with surgical drainage of CSF by whichever method rather than overdependence on a decongestant [4]. Some authors are now of the opinion that ETV may be offered as a first surgical method of treatment in TBM hydrocephalus rather than external drainage or LP drainage [5].

References

• 1 Figaji AA, Fieggen AG, Schoeman JF, Peter JC. Endoscopic third ventriculostomy in post-tubercular meningitic hydrocephalus.  Minim lnvas Neurosurg. 2006;  49 60-61
• 2 Singh D, Sachdev V, Singh AK, Sinha S. Endoscopic third ventriculostomy in post-tubercular meningitic hydrocephalus: A preliminary report.  Minim Invas Neurosurg. 2005;  48 47-52
• 3 Greitz D. Radiological assessment of hydrocephalus: new theories and implications for therapy.  Neurosurg Rev. 2004;  27 145-165
• 4 Singh D, Kurnar S. Ventriculoperitonial shunt in post-tubercular hydrocephalus.  Indian Paediatrics. 1996;  33 854-855
• 5 Husain M, Jha DK, Rastogi M, Husain N, Gupta RK. Role of neuroendoscopy in the management of patients with tuberculous meningitis hydrocephalus.  Neurosurg Review. 2005;  28 278-283

Correspondence