OBJECTIVE. The purpose of this study was to examine the frequency of change
in size of pineal cysts on serial MR studies.
MATERIALS AND METHODS. Thirty-two patients (19 females, 13 males) with a di
agnosis of pineal cyst at any time who underwent brain MR imaging more than
once in a period of at least 6 months were identified by computerized sear
ch of radiology reports. Four patients underwent MR imaging to follow up pi
neal cysts, whereas the remaining patients were imaged for a variety of ind
ications, including intracerebral neoplasms. Measurements of maximal cyst d
imension on both initial and latest follow-up studies were obtained in all
patients, and cyst volumes were calculated in 23 patients.
RESULTS. Length of follow-up ranged from 6 months to 9 years. All cysts wer
e considered incidental and none were treated. Maximal cyst dimensions rang
ed from 0.5 to 2.2 cm. On average, there was no significant change in cyst
volume. The maximal dimension of the cyst did not change in 24 (75%) of 32
patients. Two cysts resolved completely on follow-up, three cysts decreased
by 2-4 mm, two cysts enlarged by 2-3 mm, and one cyst formed and grew to 1
.2 cm.
CONCLUSION. Whereas the size of pineal cysts as a whole remained unchanged
on serial MR studies, cysts may either form or involute in individual patie
nts. Small increases in cyst size did occur but were not associated with sp
ecific clinical findings. These findings suggest that typical pineal cysts
may be followed up on a clinical basis alone rather than on imaging.