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Year : 2000  |  Volume : 48  |  Issue : 3  |  Page : 298-9

Isodense acute subdural haematoma in anaemic patients.

How to cite this article:
Deb S, Bhaumik S, Pal H. Isodense acute subdural haematoma in anaemic patients. Neurol India 2000;48:298

How to cite this URL:
Deb S, Bhaumik S, Pal H. Isodense acute subdural haematoma in anaemic patients. Neurol India [serial online] 2000 [cited 2021 Mar 7];48:298. Available from:

Typically an acute subdural haematoma appears hyperdense to brain on computerized tomography (CT) due to increased attenuation value. However, systemic diseases can complicate the CT appearance. We report a severely anaemic patient with acute traumatic isodense subdural haematoma and discuss its pathogenesis and other causes that could be responsible for different imaging findings.
A 40 year old man was admitted after a road traffic accident. He had bilateral black eye with a lacerated wound over the right forehead, along with a crush injury of the right hand that was bleeding profusely. He was opening eyes to pain, withdrawing to painful stimulus and making incomprehensible sounds. The right pupil was larger than the left and reacted poorly to light. A non contrast CT scan of the head obtained 2 hours after the accident revealed iso to hypodense area in the right frontoparietal region, with shift of the brain to left [Figure. 1]. The attenuation values at two different points in that area were 38 HU and 41 HU. The patient was taken up for surgery and approximately 40 ml of clotted subdural blood was evacuated. The patient had a haemoglobin of 5.8 gm% and a haematocrit of 16%. Other biochemical parameters, including bleeding parameters, were within normal limits.
Electron density determines the image contrast in CT scan. There is a linear relationship between CT attenuation and haemoglobin concentration, haematocrit and protein concentration. Systemic diseases can complicate the CT appearance of brain haematomas. Occasionally, acute haematomas appear isodense with adjacent brain. Acute haematomas will be isodense if the haematocrit (and therefore the protein concentration) is sufficiently low. This occurs in extremely anaemic patients when the haemoglobin concentration drops to 8-10 gm%.[1] The other conditions when an acute subdural haematoma may appear isodense with brain are disseminated intravascular coagulation (DIC) and dilution of blood with cerebrospinal fluid.[2] Our case had severe anaemia and a very low haematocrit with mainly isodense subdural haematoma. The haemoglobin level was lower than the level that corresponded to isodensity in an experimental model.[3] These cases are likely to be missed unless the index of suspicion is high and contrast enhanced scan shows a cortical vein on the surface of the brain. Other alternatives would be angiography or placement of exploratory burr holes on the swollen side. Clinicians and radiologists dealing with traumatized patients should be aware of the possibility.

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1.Boyko OB, Cooper DF, Grossman CB : Contrast enhanced CT of acute isodense subdural haematoma. AJNR 1991; 12 : 341-343.   Back to cited text no. 1    
2.Juan M. Taveras : Head injuries and their complications. In. Charley Mitchell Ed., Neuro radiology, 3rd ed. Baltimore: Williams and Wilkins. 1996; 340.   Back to cited text no. 2    
3.Smith WP, Batnidzky S, Rengachary SS : Acute isodense subdural haematomas: a problem in anaemic patients. American Journal of Roentgenology1981; 13.6 : 543-546.   Back to cited text no. 3    


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Online since 20th March '04
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