The Value Of The Ectopic Posterior Pituitary Bright Spot In The Diagnosis Of Pituitary Macroadenomas With MRI

Objective:To explore the clinical significance,imaging features and diagnostic value of ectopic posterior pituitary bright spot（EPPBS）in pituitary macroadenomas.Methods:The clinical,pathological,imaging findings of 131 patients with tumor or tumor-like lesions which invaded both intrasellar and extrasellar region were analyzed retrospectively in the Affiliated Hospital of Guizhou Medical University from February 23,2011 to December 25,2021.129 cases underwent both magnetic resonance（MR）plain scan and MR enhancement scan of the saddle region,2 cases only underwent MR plain scan of the saddle region.Clinical symptoms at admission,findings on anterior pituitary hormone and imaging findings of the patients were collected.The value of EPPBS and anterior pituitary hormones in differentiating pituitary macroadenomas from non-pituitary macroadenomas diseases were analyzed,the incidence of central diabetes insipidus（CDI）in patients with loss or ectopic posterior pituitary bright spot was counted.Results:Among the 131 patients with saddle lesions,59 were males and 72 were females,aged from 5 to 76 years old,with an average of 48.2 years old.The pathological types of 131 sellar lesions included 91 cases of macroadenomas,14 cases of meningioma,9cases of Rathke’s cleft cyst,8 cases of craniopharyngioma,3 cases of germinoma,2cases of metastatic tumor,1 case of glioma,1 case of pituitary abscess,and 1 case of pituitary eryptoeoccal ranulomagranuloma.Headache,dizziness and deterioration of visual acuity were the main symptoms at the time of visit,and the increase of prolactin（PRL）was the most common endocrine abnormality found in patients with saddle lesions.In 131 cases of sellar lesions,89 cases presented as a solid lesions,29cases presented as a cystic solid lesions,and 13 cases presented as a cystic lesions.Apart from 14 cases of Rathke fissure cyst,the other lesions were enhanced to varying degrees.EPPBS was found in 65 of 91 cases of pituitary macroadenoma,located at the distal of the pituitary stalk or the edge of the tumor outside the sellar,and presented as nodular or striped hyperintensity on T₁WI,while EPPBS was not found in the remaining 40 non-pituitary adenomas diseases.There was no significant statistical difference in the levels of thyroid stimulating hormone（TSH）,PRL,follicle stimulating hormone（FSH）,luteinizing hormone（LH）and growth hormone（GH）in pituitary macroadenoma compared with non-pituitary adenomas diseases.ROC curve analysis showed that EPPBS had diagnostic value for the diagnosis of pituitary macroadenoma（AUC=0.857,p=0.000）.43 cases with loss posterior pituitary high signal,among which 3 cases developed central diabetes insipidus preoperatively,including 1 case of germ cell tumor,1 case of pituitary metastasis,and 1 case of pituitary abscess.No central diabetes insipidus occurred preoperatively in 65 cases with EPPBS.Conclusions:EPPBS presents as nodular or striped hyperintensity at the distal pituitary stalk or tumor margin outside the sellar on T₁WI,and it is common and characteristic sign of pituitary macroadenoma.The appearance of EPPBS is helpful for the differentiation of pituitary macroadenoma from other sellar tumors or tumor-like lesions that involve both inside and outside the sellar.No specificity of anterior pituitary hormone levels in differentiating pituitary macroadenoma from non-pituitary adenomas diseases.The loss posterior pituitary high signal in T₁WI is not a specific manifestation of central diabetes insipidus,only supports the diagnosis of central diabetes insipidus.ectopic posterior pituitary tissue may be equivalent to the normal posterior pituitary in physiological function,which represents the complete function of the hypothalamic neurohypophysial axis.