Bilateral Optic Tract Enhancement: An Unusual Imaging Finding in Neurosyphilis.

CLINICAL DESCRIPTION

A 51-year-old gentleman presented to our center with intermittent blurring of vision, transient holocranial headaches, and left hemisensory disturbances of 2 months duration. Six months before onset of these symptoms, he had hematuria which was treated with oral antibiotics. After 8 weeks, he developed a diffuse maculopapular rash over the trunk involving the palms and soles. Multiple enlarged non-tender and mobile cervical lymph nodes were evident on physical examination. At the time of evaluation at our center, visual acuity and fields by confrontation were normal. The pupils were reactive, no relative afferent pupillary defect was noted, and fundi were also normal. MRI findings are depicted in [Figure 1].

Figure 1

Coronal MRI sequences (a) T2-FLAIR image showing slight enlargement of the right optic tract with central T2 hypointensity. (b) Enhancement within the both optic tracts (right > left) (c) Optic tracts isointense on T1-weighted images d. Enhancing lesion in close proximity to the left mammillary body

Cerebrospinal fluid (CSF) analysis was remarkable for a lymphocyte predominant pleocytosis (41 cells, 100% lymphocytes) and elevated protein levels (66 mg/dL). Glucose levels were within normal limits. CSF and serum venereal disease research laboratory (VDRL) and Treponema Pallidum Hemagglutination Test (TPHA) were positive (titer: 1:2560). CSF for fungal cultures; smears for abnormal cells; Acid-fast bacillus (AFB), Gram's stain, and India ink staining; standard agglutination test for Brucella antibodies; enzyme-linked immunosorbent assay (ELISA) for antimycobacterial and cysticercal antibodies were not contributory. Serum and CSF studies for anti-Aquaporin-4 and anti-myelin oligodendrocyte antibodies were also negative. Visual evoked potentials and perimetry were normal.

DISCUSSION

Syphilis affects the nervous system in 5%–30% of affected individuals. The manifestations are varied and temporally related from the time of acquisition of the infection. Commonly described clinical phenotypes are the meningovascular, neuropsychiatric, and myelopathic forms.[1] Our patient presented early in the course of the disease (within a year) and probably represented the early stages of neurosyphilis.[2] MRI lesions in the vicinity of the rostral brainstem and optic tracts were suggestive of “gummas.” In a review of 156 cases of syphilis exhibiting gummas in the brain parenchyma, 64% of lesions were located in the cerebral convexities. In this particular series, no lesion was identified in the optic tract and about 5% of the gummas were distributed in the midbrain.[3] Hemianopia with unilateral optic tract gumma has been reported in a single patient from Japan.[4] Interestingly, our patient had no objective visual field defects on testing. Our case highlights that a high degree of suspicion and meticulous history-taking are indispensable tools that can aid in the diagnosis of this rare but treatable neurological illness in the modern era. In addition, optic tract enhancing lesions in the setting of CSF pleocytosis should make one consider syphilis as a differential diagnosis.

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Conflicts of interest

There are no conflicts of interest.