We reviewed the MRI of 20 patients with a ranula (8 simple and 12 plunging)
and ten with other cystic masses in the floor of the mouth and/ or suprahy
oid portion of the neck (three haemangiomas, two neuromas, one monomorphic
adenoma, one lipoma, two lateral cervical cysts and one dermoid cyst). Hist
ological diagnoses were obtained in all cases with the exception of one pre
sumed haemangioma. Ranulas were all well-defined, homogeneous masses giving
low signal on T1-and markedly high signal on T2-weighted images. While sim
ple ranulas were all confined to the sublingual space, plunging ranulas wer
e centered on the submandibular space and tended to spill into one or more
adjacent spaces. They extended into the sublingual space anteriorly (produc
ing a so-called tail sign) in eight of 12 cases and into the parapharyngeal
space superiorly in five. Although they sometimes filled a considerable pa
rt of the parapharyngeal space, displacement of surrounding muscles or vess
els was usually slight, which was thought to reflect the nature of extravas
ation pseudocysts. All other cystic masses in our study had one or more MRI
finding different from those of ranulas and could be easily differentiated
from them.