18F-Fluorodeoxyglucose Positron Emission Tomography as a Marker of Extraocular Muscle Function.

PURPOSE: To determine whether 18F-Fluorodeoxyglucose (18F-FDG) Positron Emission Tomography (18F-FDG PET) can be utilized as a marker for extraocular muscle function, particularly in extraocular muscle paresis.

METHODS

A retrospective study was performed evaluating 18F-FDG uptake in extraocular muscles of patients with normal ocular motility across a broad age range (range 1-87 years), to establish a normative reference database. Additionally, 18F-FDG uptake was evaluated in paretic extraocular muscles and compared to the control cohort to assess whether 18F-FDG PET could demonstrate changes in metabolic activity associated with functional impairment.

RESULTS

The normative database included a total of 857 rectus muscles from 111 patients. 18F-FDG uptake declined progressively with age in all rectus muscles, with statistically significant associations for each muscle in the coronal plane. The medial and lateral recti demonstrated the steepest age-related decline in 18F-FDG uptake (P < .0005 and P <.0002, respectively). 18F-FDG uptake in 23 paretic rectus muscles from 10 patients demonstrated markedly reduced uptake compared with controls for each rectus muscle (P < .003). This difference remained highly significant when all paretic muscles were analyzed collectively using multilevel modeling (P = 9.07e-18).

CONCLUSIONS

18F-FDG PET shows promise as a surrogate marker of extraocular muscle function, particularly in hypometabolic conditions such as extraocular muscle paresis. The development of a muscle-specific normative reference database provides a foundation for broader applications of this modality, with the potential to better characterize a wide range of ocular motility disorders (NOTE: Publication of this article is sponsored by the American Ophthalmological Society).