Subdural Hematoma

Epidemiology and Etiology:

· Trauma

· Manifest within 48h after injury

· Elderly

· Demented

· In these conditions the brain is atrophied and therefore more freely mobile, and the veins are stretched more

· Infants

· Bridging veins are thin-walled

· Previous subdural hematoma

· Tend to rebleed

· Risk greatest in first few months

Common sites:

· Bridging veins from surface of cerebral hemispheres to superior sagittal sinus

· Lateral aspects of cerebral hemispheres

Gross features:

· Acute

· Freshly clotted blood along the contour of the brain surface

· No extension into depths of sulci

· Underlying brain is flattened

· Subarachnoid space is often clear

· Chronic

· Lesion is firmly attached only to the inner surface of the dura and not at all adherent to the underlying smooth arachnoid

· Lesion can eventually retract until there may be only a thin layer of reactive connective tissue (“subdural membranes”)

· Bilateral (10%)

Histologic features:

· Acute:

· 24h - Thin layer of fibrin between dura and clot

· 48-72h

· rare fibroblast at interface between dura and clot

· Fibrin only at arachnoid-clot interface

· Subacute:

· 4-5d

· RBCs begin to break down

· 2-5 cell thick layer of fibroblasts at dura-clot interface

· Occasional spindle cell within fibrin at arachnoid-clot interface

· 5-10d

· 3-14 cell thick layer of fibroblasts at dura-clot interface

· Occasional small capillaries

· Pigment-laden macrophages

· Mostly fibrin with some fibroblasts at arachnoid-clot interface

· 10-20d

· fibroblast layer 1/3 to ½ as thick as dura at dural-clot interface

· capillaries present

· pigment-laden macrophages present

· early fibroblastic membrane at arachnoid-clot interface

· Chronic:

· 3-4 weeks

· Membrane equal to dura in thickness at dural-clot interface

· Pigment-laden macrophages present

· Fibroblastic membrane about ½ as thick as dura at arachnoid-clot interface

· Occasional pigment-laden macrophages

· 5 weeks:

· Large capillaries present

· Membrane well-formed at both dural-clot and arachnoid clot interface

· 1-3 months:

· Large (giant) capillaries maybe

· Secondary hemorrhage (re-bleed)

· Hyalinization of membrane at both dural-clot and arachnoid-clot interface

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Molecular features:

·

Other features:

· Treatment is to remove the organized blood and associated organizing tissue (to prevent rebleed)

References:

· Kumar V, Fausto N, Abbas A. Robbins & Cotran Pathologic Basis of Disease, Seventh Edition. 7th ed. Saunders; 2004.