BACKGROUND:A chronic subdural hematoma is a frequently encountered entity in neurosurgical practice with highly variable incidence owing to availability of diagnostic facilities and demography of population studied. Chronic SDH is a collection of liquefied clots often encountered in  aged individuals  with atrophied brain where mild head injury can result in tearing of blood vessels resulting in gradual collection of blood and its degradation products over a period of days to weeks.

AIM:To determine the histopathologicalfeatures of outer membrane of CSDH and its association withclinico–radiological findings and postoperative recurrence .

MATERIALS AND METHODS:25 patientsdiagnosed of chronic SDH treated in the Department of Neurosurgery, Coimbatore Medical College Hospital were studied.   Their clinical and radiological findings with histopathological features of the CSDH membrane were recorded and analysed. HPE of outer membrane of CSDH were classified into four types based on the maturity and intensity of the inflammatory reaction and haemorrhage and its association with the clinico–radiological findings was assessed.

RESULTS:The common histopathological membrane was Type I (Non–inflammatory) which accounts for 40% followed by Type IV (Scar inflammatory) for 36%. Type IIand Type III membrane accounts for 12% each. Most of the patients with Type II membrane presented with GCS less than 8. Theyhad layering type of CSDH and required craniotomy for complete evacuation of hematoma. The size of the hematomas was large in Type II and Type III membranes and they had high recurrence rate.

CONCLUSION:Type II and Type III membranes are at high risk for developing neurologic deficit and have high recurrence rate hence they require craniotomy or    frequent follow up is necessary if burrhole tapping was done.