Postmalaria Labyrinthitis Ossificans: A Rare Complication of Plasmodium Infection

To the Editors: Labyrinthitis ossificans is an irreversible condition characterized by pathological ossification of the inner ear structures, being a recognized cause of permanent profound sensorineural hearing loss (SNHL).1 Its pathophysiology involves fibroblastic proliferation and secondary ossification of the inner ear following a membranous labyrinth or otic capsule endosteum insult, mainly of infectious etiology, viral or bacterial, either of tympanogenic or meningogenic origin.1 However, the association of LO and cerebral malaria is extremely rare.2 We present the case of a 12-year-old male from Angola who presented to the Neuropediatric department with a history of cognitive delay and progressive bilateral SNHL over the last 4 years. The patient's past medical history was significant for a prolonged intensive care unit hospitalization at the age of 7 years due to cerebral malaria. Up until this event, his cognitive development was unremarkable. Temporal bone computed tomography (CT) and ears magnetic resonance imaging (MRI) (Fig. 1) revealed abnormal ossification within the fluid spaces of the membranous labyrinths, more pronounced on the right, consistent with LO. Brain MRI revealed bilateral small focal gliotic areas within the brain and cerebellum parenchyma, corresponding to vascular sequelae of cerebral malaria (not shown). The diagnosis of post-malaria LO was assumed. Due to late diagnosis, the severity of the ossification contraindicated cochlear implantation. A bone-anchored hearing system was placed, with hearing recovery and adequate cognitive outcome.FIGURE 1.: Coronal (A) and axial (B) temporal bone CT shows cochlear ossification (red circles), more pronounced on the right. Axial heavily T2-weighted MRI depicts loss of the normal T2 hyperintensity of the membranous labyrinth (yellow circles), partial on the left and complete on the right.Three imaging stages of LO are described. In the acute stage (first 2 weeks), while CT is usually normal, labyrinthine contrast enhancement can be detected on MRI. In the fibrous stage (2 weeks to 2 months), early fibrous changes of the membranous labyrinth can be identified on MRI, through loss of fluid signal intensity on T2-weighted images. Finally, in the ossification stage (after 2 months), membranous labyrinth is replaced by bone, which can be easily recognized on temporal bone CT.3 Meningogenic infection spreads from the subarachnoid space to the inner ear through the cochlear aqueduct, with process starting and being more severe on the basal turn, where the aqueduct enters the labyrinth. When LO occurs secondary to a central nervous system infection, it typically presents bilaterally, unlike hearing loss of tympanic origin that presents unilaterally.4 The association between cerebral malaria and the development of LO is extremely rare and should be suspected in patients from endemic areas with SNHL. While the ototoxic effects of antimalarial drugs, particularly quinine, are well documented, the mechanism involves outer hair cell damage, microangiopathy, and ischemic injury, differently from LO.5 Early identification of LO is crucial for timely intervention and hearing preservation, imaging playing a key role on the assessment of the extension and degree of ossification. As LO progresses and ossification extends throughout the membranous labyrinth, significant challenges may arise during implant placement, potentially requiring alternative surgical techniques or devices. This case underscores the importance of considering LO as a potential long-term complication of cerebral malaria in pediatric patients. Prompt diagnosis is critical for optimizing management strategies, imaging playing a key role in its early identification.