Unique neuro-ophthalmic presentation of gun pellet injury.

We describe a unique case of orbital gunshot injury with isolated intraorbital pellets lodged symmetrically in the two apices, causing identical clinical presentation, and absence of any associated globe or cerebral injury. He developed bilateral complete third nerve palsy with bilateral traumatic optic neuropathy. The optic nerve strut prevented the pellets from going into the brain on both the sides.

Introduction

A 65-year-old male was shot as a bystander in a gunfight. The gun pellets fired from an approximate distance of 3 m (as per history), hit him on the face and upper chest. All superficial pellets were removed by a local practitioner. Immediately after the injury, the patient developed drooping of both upper lids with limited ocular movements in all directions. On elevating the eyelids, he noted the total loss of vision in both eyes (oculus uterque [OU]).

The patient presented to our hospital 6 weeks after the trauma. On examination, he was fully conscious and oriented and showed no signs of neurological deficit. Ophthalmic examination revealed visual acuity of no perception of light OU. All ocular movements expect abduction and intorsion were limited OU. Pupils were dilated and non-reactive. Fundus examination showed bilateral pale optic discs. He was diagnosed as a case of bilateral complete the third nerve palsy with bilateral traumatic optic neuropathy [Figures 1 and 2]. Cranial nerves examination revealed no other abnormality. X-ray orbit revealed 3 intraorbital foreign bodies, two in the posterior, and one in anterior orbit [Figure 3]. Computed tomography scan orbit showed very peculiarly symmetrical pellets in the region of a superior orbital fissure in the two orbits [Figure 4]. The pellets were trapped exactly at the same location (abutting the optic nerve strut) causing identical presentation in the two eyes. There was another pellet in the left anterior orbit. Interestingly, the eye globes were intact with no evidence of injury. Furthermore, no pellet was seen in the brain tissue.

Figure 1

Nine gaze pictures of the patient showing bilateral complete third nerve palsy

Figure 2

Fundus photograph showing bilateral diffuse disc pallor

Figure 3

Facial radiographs (Lateral and posteroanterior view) showing two metallic pellets embeded at both orbital apices, and one in pre septal orbital soft tissues

Figure 4

Axial (a) and coronal (b) orbital computed tomography images viewed in bone window, confirms a pellet each, located symmetrically at both orbital apices, abutting the optic nerve struts. Note that the images are degraded by the beam hardening artifacts

The patient was counseled about the visual prognosis, and no intervention was done.

Discussion

Missile head injuries causing orbital penetration is an uncommon occurrence with reported incidence of 0.6% and constitute only 1.3% cases of ocular gun pellet injuries.[12] Besides isolated orbital gun pellet injury is rare and usually co-exists with either ocular or cranial penetration.[123]

We, thus, describe a unique case of gunshot injury with isolated intraorbital pellets lodged symmetrically in the two orbits, and absence of associated globe or cerebral injury. The pellets were lodged at orbital apices, abutting the optic struts that separate the optic canal and superior orbital fissure, causing bilateral optic neuropathy and third nerve palsy.

The impact of firearm injury depends on characteristics of the projectile and anatomical structure involved. We assume in this case that the pellets entered from the medial side of orbits, traveled posteriorly nasal to globe reaching the orbital apex. Interestingly at this point, they were stopped by the optic nerve strut. Bone offer more resistance to penetration and increases the possibility of energy transfer.[45] Thus, we believe that the strut halted their further penetration into the cranium and produced a localized impact of the projectile causing damage to the second and third cranial nerves.

To the best of our knowledge, only a single case of unilateral optic nerve damage and third nerve palsy has been reported till date.[2] The identical localization of pellets in the two orbital apices causing identical bilateral presentation is an inimitable occurrence.

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Conflicts of interest

There are no conflicts of interest.