BARTONELLA HENSELAE–ASSOCIATED OPTIC NEUROPATHY PRESENTING AS A CENTRAL SCOTOMA IN THE ABSENCE OF OVERT PAPILLITIS: A MULTIMODAL IMAGING STUDY

Bartonella henselae–associated optic neuropathy may present without overt evidence of optic nerve involvement. Multimodal imaging can be critical to establishing the diagnosis.

Abstract

Background/Purpose:

The purpose of this report was to describe the use of multimodal imaging to establish the diagnosis of Bartonella henselae–associated optic neuropathy in a patient who presented with a central scotoma without overt evidence of optic nerve involvement.

Methods:

This was a case report. Main outcome measures included clinical, optical coherence tomography, and fluorescein angiography findings.

Observations:

A 72-year-old woman presented with a 3-day history of central scotoma in the left eye. Her examination was remarkable for faint exudation in the nasal macula of the left eye but was otherwise normal for her age. Spectral domain optical coherence tomography of the macula revealed mild thickening of the papillomacular bundle with scattered small cystoid spaces and several intraretinal exudates, none of which were visible clinically. Fluorescein angiography revealed localized leakage of the inferotemporal optic disc. When prompted, the patient recalled being scratched multiple times by her two pet kittens. Serial testing showed rising anti–B. henselae (B. henselae) immunoglobulin G antibody titers to 1:1,280, confirming the suspected diagnosis of B. henselae–associated optic neuropathy.

Conclusion:

Bartonella-associated optic nerve involvement can occur without overt evidence of optic disc swelling. Multimodal imaging can be used to suggest the diagnosis and support appropriate serologic testing.

Ocular infection by Bartonella henselae (B. henselae), a Gram-negative aerobic bacillus, can manifest in several ways, including Parinaud oculoglandular syndrome, focal retinochoroiditis, uveitis, vasculitis, or neuroretinitis.^1–4 Although there are many possible infectious and inflammatory causes of neuroretinitis, B. henselae infection is by far the most common etiology.⁵ Patients generally present with unilateral, painless central or cecocentral vision loss along with dyschromatopsia and are commonly found to have a relative afferent pupillary defect, optic nerve swelling, serous retinal detachment, and stellate macular exudation (macular star formation); focal retinitis or retinochoroiditis lesions may also be present.^1–4 We report an atypical case of B. henselae–associated optic neuropathy that presented with faint macular exudation without overt evidence optic disc edema, and in which multimodal imaging suggested the appropriate diagnosis.

Case Report

A 72-year-old previously healthy White woman was referred for evaluation of central scotoma in her left eye. Approximately three days before, she noted an onset of central vision loss (Figure 1D) associated with central photopsias, which she described as “fireworks” that were more prominent in the dark. Amsler grid and Humphrey visual field testing performed by the referring doctors confirmed the presence of a central scotoma. On our examination, the uncorrected visual acuity was 20/50 in the right eye and 20/200 in the left eye and improved with pinhole to 20/25 and 20/32, respectively. Intraocular pressures were normal, and there was no relative afferent pupillary defect, as confirmed by multiple ophthalmologists. Examination of the anterior segments found mild nuclear sclerosis of the lenses but was otherwise unremarkable. Examination of the posterior segment only identified faint exudation in the nasal macula (Figure 1A). Spectral domain optical coherence tomography of the macula showed mild thickening of the papillomacular bundle with fine intraretinal exudates and scattered small cystoid spaces (Figure 1C) that were not clinically visible. Fundus autofluorescence was unremarkable (not shown). Fluorescein angiography identified a focal, well-circumscribed area of hyperfluorescence involving the inferotemporal optic disc (Figure 1B). On further questioning, the patient denied any history of eye surgeries and use of systemic medications or supplements other than daily multivitamins, but shared that she was raising two kittens, and had been scratched on multiple occasions. We screened her for anti–B. henselae antibodies three weeks after the onset of symptoms, but they returned normal, as did the serology for syphilis, tuberculosis, and sarcoidosis. Owing to high suspicion for cat-scratch disease, we repeated the antibody panel along with a Toxoplasma gondii antibody panel five weeks later, and the results showed normal anti–B. henselae IgM levels, elevated anti–B. henselae immunoglobulin G titers (1:1,280), and no evidence of anti–T. gondii antibodies. The patient was treated with a five-day course of oral azithromycin, and when she returned nearly three weeks later, her visual acuity improved and she described a reduction in the size and severity of her central scotoma in the left eye. At the most recent follow-up encounter, two-and-a-half months after presentation, her uncorrected vision was 20/50 with pinhole to 20/32 in the left eye and she continued to have a symptomatic paracentral scotoma. The patient's presenting posterior segment findings remained unchanged, but repeat fluorescein angiography revealed less intense focal hyperfluorescence of the optic disc (not shown).

Fig. 1.

A. Fundus photograph of the left eye showing faint exudation in the nasal macula. B. Midphase fluorescein angiogram of the left eye showing localized leakage from the inferotemporal optic disc. C. Spectral domain optical coherence tomography of the left eye showing thickening of the papillomacular bundle with several intraretinal exudates and scattered small cystoid spaces. D. 24-2 Humphrey visual field of the left eye documenting a central scotoma.

Discussion

Our patient presented with acute central vision loss in her left eye. There was no detectable relative afferent pupillary defect on serial testing, and the only notable abnormality on examination was the presence of faint intraretinal exudation in the nasal macula of the left eye. Imaging with spectral domain optical coherence tomography revealed mild thickening of the papillomacular bundle associated with scattered intraretinal exudates and small cystoid spaces that were not evident on clinical examination. Angiography revealed leakage from the inferotemporal quadrant of the optic disc in the affected eye and serial anti–B. henselae antibody testing revealed rising titers to 1:1,280 over eight weeks after the onset of symptoms.

A thorough clinical history and examination along with directed ancillary testing and serology are often necessary to uncover the etiology of rapid vision loss from optic neuropathy, which can be caused by demyelination, inflammation, ischemia, or trauma.⁶ Eyes with optic neuritis may have a normal-appearing optic disc, but patients often report associated dyschromatopsia, periorbital discomfort, and pain with eye movement and may have a history of paresthesia, limb weakness, or decreased vision with increased body temperature.⁶ Magnetic resonance imaging of the brain and orbits will show enhancement of the optic nerve and possibly of the white matter, as well.⁶ Elderly patients with vision loss associated with pallid disc edema and concurrent symptoms of temporal headache, jaw claudication, unexplained weight loss, and myalgia should be considered to have arteritic ischemic optic neuropathy until proven otherwise.⁶ The presence of an elevated erythrocyte sedimentation rate or choroidal infarction on fluorescein angiography are strongly suggestive diagnostic measures, but a temporal artery biopsy showing granulomatous inflammation of all layers remains the gold standard because of its 100% specificity.⁶ Meanwhile, the presence of severe disc edema with hemorrhages in a patient with multiple vascular risk factors and a “disc-at-risk” (cup-to-disc ratio of 0.1 or less) in the contralateral eye is characteristic of nonarteritic ischemic optic neuropathy.⁶ Humphrey visual field testing in these patients typically shows an arcuate or altitudinal visual field defect.⁶ When a history of craniofacial trauma precedes vision loss in a patient with a relative afferent pupillary defect, traumatic optic neuropathy is the likely diagnosis. Optic nerve involvement has also been described in a variety of autoimmune and infectious disorders such as syphilis, sarcoidosis, granulomatosis with polyangiitis, systemic lupus erythematosus, inflammatory bowel disease, Behçet disease, Lyme disease, and cat-scratch disease, and serologic testing for these conditions should be considered.⁶

The optic nerve head is long believed to be the first target of acute neuroretinitis.⁷ Previous reports on Bartonella-associated neuroretinitis have generally described either diffuse or sectoral optic disc edema, or papillitis, with or without stellate macular exudates.^8,9 Suhler et al⁹ described one case of B. henselae–associated neuroretinitis in whom the optic disc involvement was visible on fluorescein angiography, suggesting that clinical optic disc edema was not evident—although this was not stated specifically and no imaging was provided. The pathogenesis of sectoral and subclinical papillitis in certain patients is unclear but may represent a very limited form of localized involvement.⁸ Retrobulbar optic nerve involvement has been observed on magnetic resonance imaging of the orbits in patients with active Bartonella-associated neuroretinitis,¹⁰ and it is possible that the optic nerve inflammation in certain patients with neuroretinitis is predominantly retrobulbar. In patients with high clinical suspicion for B. henselae–associated optic neuropathy, a single acute negative titer may be insufficient to exclude diagnosis and convalescent titers as soon as two weeks later can show seroconversion.¹¹

In summary, Bartonella-associated optic neuropathy can be subclinical and difficult to diagnosis. Multimodal imaging may reveal evidence of limited optic disc involvement, supporting the use of directed laboratory testing to assess for causes known to cause acute inflammatory optic neuropathy, including B. henselae infection.