The value of Tc99m-MDP bone scan and SPECT/CT in the diagnosis of metastatic carcinoid rectal cancer with hypoglossal nerve palsy.

Objectives: The authors present a case of Hypoglossal Nerve Palsy from Metastatic Carcinoid Rectal Cancer.

Methods: The patient is an 81-year-old female presenting with a history of headache, localizing to the left occipital region extending to the left lower neck and weakness of the tongue and difficulty articulating for approximately 5 months. The patient has a past history for intermediate grade neuroendocrine tumor of the rectum with metastasis to the liver and bone. F-18-FDG PET/CT scan from the level of the mid orbits to the mid thighs was obtained, and the images showed asymmetric FDG activity of the base of the tongue but no focal increase in activity in the soft tissue or bone in the remainder of the head and neck. An MRI of the neck with and without gadolinium was obtained which showed atrophy of the left tongue base affecting the intrinsic and extrinsic muscles. The content of and the signal intensity of the left hypoglossal canal was asymmetric when compared to the contralateral side, with evidence of sclerosis of the left jugular tubercle. Although there was no definite evidence of tumor along the tract of the left hypoglossal nerve, perineural tumor could not be excluded. A correlating Tc99m-MDP bone scan with SPECT-CT was obtained, which showed intense increase in radiotracer activity with corresponding sclerotic changes starting at the posterior left aspect of the sphenoid bone extending caudally terminating in the C1 vertebral body on the left. There was evidence of involvement of the medial aspect of the hypoglossal canal.

Results: The patient underwent subsequent treatment of external beam radiation to the skull base following the Tc99m-MDP bone scan with SPECT-CT. At approximately 5 months’ post radiation treatment the patient reported complete resolution of her headaches and partial improvement of her tongue weakness, with some associated loss of taste. The follow-up imaging showed no identifiable asymmetry of the left hypoglossal canal or left aspect of the clivus.

Conclusion: This case illustrates the value of Tc99m-MDP with SPECT-CT imaging for correlation with MRI asymmetry suspicious for perineural tumor from adjacent boney structure. Research Support: