Left is right and right is wrong: Fluorodeoxyglucose uptake in left hemi-diaphragm due to right phrenic nerve palsy
A 36-year-old Indian male, underwent whole body FDG PET/CT for staging of recently diagnosed right lung carcinoma. He complained of cough and difficulty in breathing since last 3 weeks. The PET/CT scan showed increased FDG uptake in right perihilar lung lesion [black arrow in and red arrows in ] compatible with known lung neoplasm. There was no abnormal FDG uptake in the mediastinal lymph nodes. Maximum intensity projection image also showed increased FDG uptake in accessory muscles of respiration-bilateral sternocleidomastoid and inter coastal muscles [blue arrows in ] and unilateral, intense FDG uptake in left hemi-diaphragm [red arrows in Figure and ]. On CT, there was no morphological abnormality in any of the above-mentioned muscles with FDG uptake. Coronal CT image revealed elevated right hemi-diaphragm [arrow in ], suggestive of right diaphragmatic paralysis. Fused PET/CT image [coronal slice, arrow in ], shows intense FDG uptake in left hemi-diaphragm. The maximum standardized uptake value of this uptake was 6.1 (normalized for body surface area). These FDG PET/CT findings suggested a cause-effect relationship, indicating right phrenic nerve palsy caused by the lung neoplasm resulting in right diaphragmatic paralysis. This possibly resulted in asymmetric, intense FDG uptake in the left hemidiaphragm and accessory muscles of respiration, due to compensatory increased workload related to contralateral right diaphragmatic paresis.