Ans. a (Middle meningeal artery). (Ref: B & L, Surgery, 25th/ 303).Extradural haematoma (EDH)# It is a neurosurgical emergency. An EDH is nearly always associated with a skull fracture and is more common in young male patients. The skull fracture is asso- ciated with tearing of a meningeal artery and a haematoma accumulates in the space between bone and dura. The most common site is temporal, as the pterion is not only the thinnest part of the skull but also overlies the largest meningeal artery - the middle meningeal.# An EDH may also occur in other regions such as frontal as well as in the posterior fossa. They are not always arte- rial: disruption of a major dural venous sinus can result in an EDH. The force required to sustain a skull fracture can be surprisingly small - a fall from standing or a single blow to the head.# The classical presentation of an EDH, occurring in less than one-third of cases, is initial injury followed by a lucid interval when the patient complains of a headache but is fully alert and orientated with no focal deficit. After minutes or hours a rapid deterioration occurs, with contralateral hemiparesis, reduced conscious level and ipsilateral pupillary dilatation as a result of brain compression and herniation.FEATUREEDH (EXTRADURAL HEMATOMA)SDH (SUBDURAL HEMATOMA)Incidence1-4%10-20%EtiologyLacerated middle meningeal artery/ dural sinus in 70 to 85% cases.Stretching, tearing of bridging cortical veins.AgeAnyOlder peoplefractureSeen in 85-95% cases-LocationBetween skull & dura.95% supratentorialCrosses dural attachments but not sutures.Between dura & arachnoid95% supratentorialCrosses suture but not dural attachmentBilateral5%15%CT- Biconvex (lentiform shape)- 2/3 hyperdense (- 1/3 mixed density)- Displace greywhite interfacea) Acute SDH: Crescentic & hyperdenseb) Subacute SDH: May be nearly isodense with cortex neo-membrane, underlying vessels may enhance.c) Chronic SDH: Hypodense with enhancing membrane. About 1-2% of very old SDH calcify