"Guitar pick sign" on MRI.

A 60-year-old male who presented with right orbital pain, swelling, and watering for 5 days showed right proptosis, redness, swelling, restricted extraocular movements and no light perception. Magnetic resonance imaging orbits showed extensive right retrobulbar inflammation and T2 hypointense signal causing significant proptosis and stretching of the optic nerve which in turn deformed the posterior globe into a characteristic “guitar pick” shape [Figs. 1 and 2]. Surgical debridement showed Aspergillus infection, following which antifungal treatment was instituted. Posterior globe tenting also called as “guitar pick” sign is usually seen in orbital trauma and acute inflammatory/infective pathologies.[123] Significant proptosis stretches the optic nerve which tethers the globe and damages the optic nerve either due to acute stretching or acute ischemia. Posterolateral canthotomy and inferior cantholysis can relieve posterior globe tenting in cases of retrobulbar haemorrhage.[2] Aggressive surgical debridement along with antifungal therapy is useful for treating fungal infections presenting with retrobulbar disease.[3] Drainage of orbital hematoma or abscess and bony wall decompression may also help. Identifying the “guitar pick” sign sonographically may add to the clinical examination and help decide whether to perform decompression. As “guitar pick” sign on imaging (especially when posterior angle is <120°) is associated with acute and permanent visual damage, it should prompt urgent treatment.[123]

Figure 1

MRI orbit axial section (a) shows posterior globe tenting (“guitar pick” sign) with significant retrobulbar inflammatory changes on the right side (white arrow). Coronal section (b) shows significant retrobulbar inflammatory changes on the right side (white arrow)

Figure 2

MRI orbit sagittal section (a) shows posterior globe *** tenting (“guitar pick” sign) with significant retrobulbar inflammatory changes on the right side (white arrow). Sagittal section of left eye (b) shows normal posterior surface of globe and normal retrobulbar fat (white arrow)

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