Rathke Cleft Cyst Workup
The initial workup for a suspected Rathke cleft cyst requires MRI of the sella with and without IV contrast using thin-slice pituitary protocol sequences, comprehensive pituitary hormone assessment including basal and dynamic testing, and formal visual field examination. 1
Imaging Protocol
MRI is the gold standard and mandatory first-line imaging modality for evaluating suspected Rathke cleft cysts. 1
Required MRI Sequences
- Obtain pre-contrast T1-weighted and T2-weighted thin-slice (2 mm) sequences through the sella 1
- Add post-contrast T1-weighted sequences with gadolinium to distinguish Rathke cleft cysts from small pituitary adenomas, which may be occult without contrast 1
- Include post-contrast volumetric gradient echo sequences to increase sensitivity for detecting small lesions and defining anatomical relationships 1
- Use 3-Tesla MRI when available for superior anatomical delineation, particularly for surgical planning 1
Key Imaging Features to Document
- Cyst size and exact location (intrasellar vs. suprasellar extension) 2, 3
- Presence of hemorrhage or fluid-fluid levels 4, 5
- Pituitary stalk position and compression 6
- Optic chiasm displacement or compression 1, 3
- Sellar floor integrity and sphenoid sinus involvement 7
CT has no role in the initial workup of Rathke cleft cysts as it provides inadequate soft-tissue detail of intrasellar and parasellar structures. 1
Endocrine Evaluation
Perform comprehensive pituitary hormone assessment in all patients with suspected Rathke cleft cysts, regardless of cyst size, as even microadenomas can rarely cause hypopituitarism. 6, 3
Required Hormonal Testing
- Basal hormone levels: morning cortisol, ACTH, free T4, TSH, prolactin, IGF-1, testosterone (males), estradiol and LH/FSH (premenopausal females) 1, 3
- Dynamic pituitary testing when basal levels suggest deficiency 1, 6
- Assess all pituitary axes systematically as panhypopituitarism occurs in 18-36% of patients with cysts ≥10 mm 2, 3
Clinical Context for Endocrine Testing
- Cysts <10 mm rarely cause hormone deficiencies (only 2.9% affected) 2
- Cysts ≥10 mm have significantly higher rates of hypopituitarism (18-36%) 2, 3
- Hypopituitarism from Rathke cleft cysts typically does not recover after surgery (only 14-50% show partial improvement), making preoperative documentation critical 3, 8
Visual Assessment
Obtain formal visual field testing and visual acuity measurement in all patients with Rathke cleft cysts, particularly those with suprasellar extension. 1, 3
Visual Testing Requirements
- Formal perimetry (automated visual field testing) to detect subtle chiasmal compression 1
- Visual acuity testing using standardized methods 1
- Document baseline visual function as 45% of surgical patients have visual field defects and 20% have impaired visual acuity at presentation 2
Clinical Symptom Assessment
Key Symptoms to Document
- Headache pattern and severity (present in majority of symptomatic cases) 3, 8
- Acute onset symptoms (within 7 days) suggesting hemorrhage, inflammation, or infection mimicking pituitary apoplexy 5
- Visual changes including blurred vision, diplopia, or ptosis 4, 5
- Polyuria suggesting diabetes insipidus 5
- Fever or general malaise suggesting inflammatory or infectious complications 5
Size-Based Risk Stratification
Cyst size determines both the likelihood of symptoms and the appropriate follow-up strategy. 2, 8
Cysts <10 mm
- Low risk for progression (stable over 5 years in 97.1%) 2
- Hormone deficiencies rare (2.9%) 2
- Visual impairment uncommon (2%) 2
- Radiological follow-up can be limited to 5 years if asymptomatic 2
Cysts ≥10 mm
- Higher risk of symptoms (18% hormone deficiency, 5.7% visual impairment) 2
- Paradoxically may decrease in size over time without intervention 2
- Require longer surveillance due to potential for delayed complications 2, 8
Critical Diagnostic Pitfalls
Rathke cleft cysts with acute presentation can mimic pituitary apoplexy and require urgent surgical evaluation. 5
- MRI rim enhancement in acute cases suggests hemorrhage, inflammation, or abscess formation 5
- Intraoperative frozen sections may be ambiguous due to overlapping features with craniopharyngioma, particularly when squamous metaplasia is present 4
- Squamous metaplasia in the cyst wall increases recurrence risk and may represent a transitional state toward craniopharyngioma 4, 8
Differential Diagnosis Considerations
The imaging workup must distinguish Rathke cleft cysts from other sellar masses including pituitary adenomas, craniopharyngiomas, and arachnoid cysts. 1, 7