A 38 y.o construction worker with a hx of Graves disease presents with central vision loss in the R eye.

He has exophthalmos from his previous Graves disease and an MRI is ordered.

what is the differential for hypopigmented spots in the retina?

Our patient had syphilis which causes, among other things, a pan uveitis of the eye.   In the posterior aspect of the eye this can result in both optic disc edema and hypopigmentation in the retina.  This leads to decreased visual acuity and can cause blindness. Our patent had an RPR of 1:128.

For review, this is a normal retina. The macula appears red if there is central retinal artery occlusion because the rest of the retina is ischemic and whitish.

 Papilledema or swelling of the optic disc also frequently occurs in the setting of increased intracranial pressure.  This can occur in many medical conditions including:  brain tumors, chiari malformations, pseudotumor cerebri,  sinus thrombosis  and brain hemorrhage.

Papilledema can be difficult to recognize on fundoscopic exam in the early stages.   It begins with blurring of the nasal portion of the disc. It progresses to swelling of the optic nerve and then frank hemorhages in the retina.

early papillema shows blurring on the nasal side of the disc

On initial exam our patient was noted to have macular edema, mild disc edema and inflammation in multiple segments of the retina with  a hypopigmented area  over the macula. This led to a diagnosis of posterior uveitis with a differential including the usual suspects. sarcoid, syphilis, toxo and HIV.   

In the early stages  of papilledema MRI can be a useful tool in making the diagnosis with enlargement of the optic nerve sheath, flattening of the posterior sclera and protrusion of the optic papilla into the globe or tortuosity of the optic nerve.  Ultrasound can also be a useful tool but both an optic nerve sheath diameter of >6 mm(3mm from the retina) and edema of the optic head should be present.

papilledema on MRI

papilledema on US is most convincing with both the elevated optic nerve and widened optic nerve sheath.

Fun fact

Color vision is dependent on both the optic nerve and the macula.  In MS with optic neuritis the color red may be washed out or gray.

Our patient was treated for syphilis.   With IV pen G  q 4 for two weeks. The patient also noted hearing loss in the L ear which is also possibly related to syphilis.

 Passi N, Degnan A, Levy L MR imaging of papilledema and visual pathways: effects of increased intracranial pressure and pathophysiologic mechanism.  AJNR Am J Neuroradiol 2013 May;34(50:919-924.

Lochner P, Brio F, Zedde M, et al.  feasibility and usefulness of ultrasonography in ideopathic intracrenail hypertension or secondary intracranial hypertension. BMC Neurol 2016;16:85.

https://emcrit.org/pulmcrit/pulmcrit-algorithm-diagnosing-icp-elevation-ocular-sonography/