Membrane surface-area:volume ratio in Chronic Subdural Haematomas.'Critical size' and potential post-operative target.

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Membrane surface-area:volume ratio in Chronic Subdural Haematomas.'Critical size' and potential post-operative target.

World Neurosurg. 2017 Jan 17;:

Authors: Manickam A, Marshman LA, Johnston R

Abstract
BACKGROUND: It is unknown why some chronic subdural haematomas (CSDH) grow and require surgery, whilst others spontaneously resolve. Although a relatively small CSDH volume (V) reduction may induce resolution, V% reduction is often unreliable in predicting resolution. Whilst CSDH evolve distinctive inner and outer neo- membranes (IM and OM), the OM likely dominates the dynamic growth-resorption equilibrium. If other factors remain constant, one previous hypothesis is that resorption could fail as the surface area (SA):V ratio decreases when CSDH exceed a 'critical size'. We aimed to identify a 'critical size', and an ideal target, which implies resolution without recurrence.
METHODS: Three-D CT CSDH SA:V ratios were obtained using computer software to compare CSDH SA:V between cases requiring surgery ('surgical') and cases managed conservatively with spontaneous resolution ('non-surgical').
RESULTS: Data was obtained in n=45 ('surgical':'non-surgical' 28:17). CSDH risk factors did not significantly differ between 'surgical' and 'non-surgical' cases. 'Surgical'-V was 2.5x'non-surgical'-V (119.9±33.1ml v 48.4ml ±27.4ml, P<0.0001). 'Surgical'-total-SA was 1.4x'non-surgical'-SA (256.63±70.65cm(2)v 187.67±77.72cm(2), P=0.004). 'Surgical'-total-SA:V was approximately one-half that of 'non-surgical'-SA:V (2.14±0.90 v 3.88±1.22ml(-1), P<0.0001). 'Surgical' OM-SA (SAOM) was 120.63±52cm(2), 'non-surgical'-SAOM was 94.10±41cm(2) (P<0.0001). 'Non-surgical'-SAOM:V was 1.94ml(-1) whilst 'surgical' SAOM:V was 1.005ml(-1): i.e. 'surgical' SAOM ≈V.
CONCLUSIONS: Because 'surgical'-total-SA:V≈2:1, one neo-membrane may indeed dominate the dynamic growth-resorption equilibrium. CSDH 'critical size' thus appears to be when SAOM≈V, which is intuitive. Practically, subtotal CSDH evacuation which approximately doubles total SA:V or SAOM :V implies CSDH resolution without recurrence. This could guide subdural drain removal timing, discharge or transfer. Prospective validation studies are required.

PMID: 28108426 [PubMed - as supplied by publisher]

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