Cerebral protothecosis mimicking high-grade glioma

Abstract

Prototheca wickerhamii is a common, indolent alga that seldom causes central nervous system infections in humans. We report the first UK case of cerebral protothecosis in an immunocompetent 56-year-old woman who presented with a 5-month history of intermittent fatigue followed by a 2-week history of symptoms, including right arm and leg weakness, a loss of fine motor coordination, worsening gait, right facial tingling, diplopia and a metallic oral taste. MRI scans revealed a multifocal abnormality suggestive of high-grade glioma. Given the clinical presentation, absence of immunodeficiency and characteristic MRI features, a diagnosis of high-grade glioma was deemed most likely by the multidisciplinary team. Surgical biopsy provided material for histopathological and microbiological diagnosis. She underwent a 2-year course of antimicrobials with surveillance MRI scans. The patient made a good functional recovery but still retains mild neurological sequelae.

Keywords: infection (neurology); infectious diseases; neurosurgery; radiology.

Figure 1

Pre-biopsy MRI: (A and B) Pre-GAD non-contrast T1-weighted images and post-GAD contrast T1-weighted images, respectively. Subtle contrast enhancement can be seen over the right striatal lesion. (C) T2-weighted image showing right striatal central hypointensity surrounded by the associated high signal intensity with mild effacement of the lateral ventricle. Subtle increased signal intensity over the left thalamic region. (D) FLAIR image showing periventricular signal change and signal intensity over the left thalamic area. (E and F) DWI image with corresponding ADC map showing restricted diffusion centrally and subtly within the left thalamic region. [ADC, apparent diffusion coefficient; DWI, diffusion-weighted imaging; FLAIR, fluid attenuation inversion recovery].

Figure 2

(A) Biopsy section stained with Haematoxylin and Eosin (H&E) stain showing granulomatous inflammation with histiocytic giant cells and macrophages. (B) Periodic acid–Schiff stain demonstrating protothecal morula-like structures with endospores. (C) ×800 direct magnification of spherical morula-like structures, typical of Prototheca wickerhamii. (D) ×4000 direct magnification of a single protothecal morula with multiple endospores and a clear outer cell wall.

Figure 3

Six-week serial MRI: (A) T1 + GAD-weighted image demonstrating the formation of a thick ring-enhancing lesion in the right caudate region. (B) T2-weighted sequences revealed progressive vasogenic oedema surrounding the right striatal lesion with improvement to the prior subtle left thalamic signal change. (C and D) FLAIR and ADC sequences demonstrating progressive vasogenic oedema with central restricted diffusion over the right striatal lesion. [ADC, apparent diffusion coefficient; FLAIR, fluid attenuation inversion recovery].

Figure 4

Six-month MRI: (A) T1 + GAD sequences demonstrating a reduction in the overall size of the ring-enhancing right striatal lesion but with the progression of the left thalamic ring-enhancing lesion. (B) T2-weighted sequences demonstrating reduced surrounding right striatal vasogenic oedema and localised signal change surrounding the left thalamic lesion. (C and D) FLAIR and ADC sequences showing central restricted diffusion of the right striatal lesion and reduced vasogenic oedema. Increases of FLAIR signal over the left thalamic lesion can be seen. (E and F) T1+GAD and T2-weighted images of cerebellum displaying left cerebellar signal change with enhancement indicating avid leptomeningeal involvement. [ADC, apparent diffusion coefficient; FLAIR, fluid attenuation inversion recovery.