ANATOMY - HAEMATOMA

Question 1

Motorbike rider involved in a serious accident. In considerable pain and with suspected fractures of his limbs. Initially conscious and able to talk. However, as he was being observed and treated, he suddenly became very drowsy. It was only then that the staff in the Trauma Unit that there was bruising on his left temple. A radiograph of his skull revealed a fracture running down the squamous part of the temporal bone and across the base of the middle cranial fossa. His left pupil was dilated, but not the right pupil, and there was weakness of his facial musculature. An emergency CT scan showed blood collecting around the lateral aspect of the left cerebral hemisphere (see picture, on right)

Name the lesion that you see on the CT scan (arrowed) [1]

Answer 1

Epidural haematoma

Question 2

Describe the aetiology of this lesion in this accident [2]

Answer 2

Squamous part of temporal bone is very thin and prone to fracture (1). Rupture of middle meningeal artery within the cranial cavity causes a haematoma (1).

Left compression skull fracture of the pterion, leading to laceration of the left MMA

Question 3

Describe two possible aetiological processes that may have caused the facial palsy [2 each = 4]

Answer 3

Haematoma compresses primary motor cortex that provides input to the nuclei of CN VII (2)

The fracture may have caused direct damage to left CN VII as it passes through the internal acoustic meatus or facial canal (2)

UMNL: Compression of the facial nerve between cerebrum & cerebellum as it exits the pons d/t the epidural haematoma causing an increase cerebral pressure

LMNL: Laceration of the facial nerve directly due to trauma as it exits the skull through the mastoid foramen or distally

Question 4

Explain the unequal sizes of the patient’s pupils [2]

Answer 4

Compression of the left oculomotor nerve (CN III) & disruption of the parasympathetic supply to the sphincter of the pupil.

Compression of the PNS division of the CN III occurs first, before compression of the motor division of the CN III, because the PNS division is thought to run on the outside or peripheral cuff of the CN III. Therefore, with ICP, external compression of the nerve at sites of possible constriction e.g. the exit foramina for the nerves. Also, the left side is greatly affected, as the extradural haematoma is causing a midline shift, stretching and compressing the left CN III greater than the right.

Question 5

Why did the patient become drowsy after a period of time had elapsed? [1]

Answer 5

ICP  Compression of the reticular activating centre in the mesencephalon and diencephalon

Question 6

What immediate surgical intervention must be exercised to relieve the main problem? [1]

Answer 6

Drilling of a burr hole through the left temporal bone and drainage of the blood clot (1). Also accept the administration of a diuretic e.g. mannitol while you prepare for the burr holes (NB immediate intervention)

Drain the epidural haematoma, and repair the lacerated middle meningeal artery

Question 7

Comment on the changes in position (alignment) of the intracranial structures shown on the patient’s CT scan [1]

Answer 7

Structures displaced to the right. Epidural haematoma has caused a midline shift on CT to the right.

Question 8

If the condition were left to deteriorate, describe what further damage would occur to the patient’s brain and the effects thereof [3]

Answer 8

Displacement of the brain stem to the right  compression of the right crus cerebri (corticospinal tract); left-sided hemiplegia; eventual death because of compression of medulla (4)

Obstructive hydrocephalus – blockage of cerebral aqueduct

Herniation of cerebellar tonsils, tentorial or subfalx. Have blood supply  congestion, oedema, infarction, then haemorrhage

Epilepsy: Stretching of the neurones leads to irritability & spontaneous & continuous discharge of neurones which can lead to cell death via excitotoxicity

Question 9

18 m/o girl with viral bronchiolitis admitted for regular observation overnight. In the early hours of the morning, she rolls over and falls out of the cot onto the floor, injuring the side of her head badly. As the night passes she continues to cry and has begun to vomit. She is showing anisocoria (unequal sizes of pupils) and her level of consciousness appears decreased. Dr concerned about the way she is gasping for air & immediately sends her for a CT scan of her head. One of the images is recorded on the right:

Explain the process leading to anisocoria (2)

Answer 9

Raised ICP leading to compression of CN III – affects parasympathetic supply to intrinsic muscles of eyeball – unequal sizes of pupil (sphincter of pupil)

Question 10

Briefly explain three other changes that could be noted in a child or an adult with respect to the eyes that may lead one to conclude that there is raised intracranial pressure (6)

Answer 10

Strabismus – CN III, IV and/or VI – extrinsic muscles of eyeball - RL6SO4

Possibly ptosis – CN III – levator of upper eyelid

Possibly difficulty in focusing – changing shape of lens – CN III – ciliary body

Papilloedema – oedema of retina caused by constricted venous drainage – raised ICP transmitted along the optic tract to back of eyeball, because dura around optic tract is fused to sclera

Also accepted: Decreased level of consciousness, unresponsive pupillary reflex, blurred vision, headache, nausea, signs of cerebellar dysfunction [that’s not in the eyes, can’t even read their own question]