A 20 year old man attended the accident and emergency department after an assault with a short bladed knife. He had sustained a stab wound to the right orbit. There was no other significant history. On examination he was alert and orientated with a Glasgow coma scale of 15. Snellen visual acuities were no perception of light right eye and 20/20 left eye. Inspection of the right orbit revealed a right upper lid laceration and an underlying penetrating eye injury. There was no other neurological deficit. Plain orbital radiographs were obtained but did not show any defects. However, in view of the nature of the injury and the fact that the posterior extent of the orbital wound could not be visualised, a computed tomogram of the head was obtained. This showed pronounced pneumocephalus (fig 1). A fracture of the posterior wall of the frontal sinus was noted with a fracture line through the ethmoidal labyrinth extending to the medial wall of the left orbit. A fragment of bone was seen to abut the left medial rectus muscle (fig 2). The patient subsequently underwent anterior cranial fossa repair by the neurosurgeons and repair of the penetrating eye injury by the ophthalmologists. He made an uneventful recovery after surgery. There was, however, no improvement in the visual acuity of the right eye as a result of total retinal detachment with proliferative vitreoretinopathy.

• Download figure
• Open in new tab
• Download powerpoint

Figure 1

 Computed tomogram of the head showing pneumocephalus with fracture of posterior wall of frontal sinus.

• Download figure
• Open in new tab
• Download powerpoint

Figure 2

 Computed tomogram of the head showing fracture line through ethmoidal labyrinth extending to medial wall of left orbit with fragment of bone abutting left medial rectus. The right penetrating eye injury can also be seen.

DISCUSSION

The orbit is pyramidal in shape with a quadrangular base situated at the orbital margin. The walls of the orbit are thin and may be penetrated by objects moving at some velocity directed at right angles to the wall. The roof of the orbit that is made up of the frontal bone and the lesser wing of the sphenoid is very thin and is therefore at particular risk of injury, especially in children who fall on sharp objects carried in the hand.^1,2 Penetration of the orbital walls may result in damage to the paranasal sinuses, which may give rise to emphysema of the orbit, cerebrospinal fluid fistulas, orbital cellulitis, meningitis, cerebral abscess, or pneumocephalus. The intracranial complications of transorbital stab wounds include ventricular damage, carotid-cavernous sinus fistula, pneumocephalus and subdural, subarachnoid, intraventricular, and intracerebral haemorrhage.

Orbital radiographs may be negative and are therefore unreliable in ruling out intracranial involvement, as in our case.^2,3 Furthermore, initially there may be no apparent neurological deficit on examination, and therefore a lack of neurological signs does not exclude a secondary brain injury.³ In summary, orbital stab wounds may mask serious underlying intracranial injuries and therefore we would recommend that computed tomography is performed in cases where there is any suspicion of a secondary transorbital brain injury.