Fig. 36.1
Magnetic resonance imaging (MRI) appearance of Rathke’s cleft cyst (RCC), with sagittal (a) and coronal (b) T2-weighted images. Note lesion rising out of sella (black arrow) and compressing optic chiasm (white arrow)
Pars intermedia cysts are embryonic fluid-filled cavities between the adenohypophysis and neurohypophysis. They differ from RCC in not being derived from Rathke’s pouch, not being lined with epithelium, and generally not enlarging over time [5, 6].
Pathophysiology
All lesions of this region can cause symptoms by local mass effect, compressing the optic apparatus (classically causing a bitemporal hemianopsia), the hypothalamus (causing obesity), the third ventricle (causing hydrocephalus), or the cavernous sinus (causing injury to the cranial nerves with visual or pain complaints).
Adenomas can cause symptoms by overexpression of specific hormones or—in larger lesions—impairment of glandular function by mass effect (commonly manifested as growth arrest or impaired sexual maturation) .
Rarely, pituitary lesions can present with apoplexy, although this is far less common in children than in adults .
Molecular/Genetic Pathology
Incidence and Prevalence
Secretory adenomas that produce growth hormone (GH) and adrenocorticotropic hormone (ACTH) are most common in preadolescent children, while prolactin-secreting adenomas are most common in older children (and are also the most common overall, at nearly 50 %, of all adenomas in children).
RCCs are found in up to 25 % of all adults, implying a similar number in children [6].
Age Distribution
GH-producing adenomas are most common in infants, while all other adenomas tend to present across all ages, with some reports suggesting an increased detection (up to 66 % of all adenomas) during teen years [4].
Sex Predilection
Geographic Distribution
None
Risk Factors—Environmental, Life Style
None
Relationships to Other Disease States, Syndromes
MEN-1 has been associated with adenomas, although it remains extremely rare in children .
RCCs are often found in association with adenomas, although some have suggested that this is a “bystander” effect, in which a symptomatic adenoma is what prompts imaging, and then an incidental finding of a RCC is noted (given the high incidence in the general population of RCC at about 25 %, see above) .
Presentation
In general, lesions of this region are either found incidentally or present in one of three ways. These include:
Visual loss (usually bitemporal hemianopsia from chiasmal compression)
Endocrine or hypothalamic dysfunction (from tumoral hormone production or injury to the hypothalamus)
Symptoms of mass effect in the sellar region (headache, hydrocephalus, and dysfunction of the cranial nerves in the cavernous sinus leading to double vision or facial pain)
Differential Diagnosis
The differential diagnosis of lesions in the pituitary region in children include :
Adenoma
RCC
Pars intermedia cyst
Craniopharyngioma
Germinoma/nongerminomatous germ cell tumors
Optic pathway tumor
Lipoma
Dermoid/epidermoid
Arachnoid cyst/encephalocoele
Lymphocytic hypophysitis/infection (tuberculosis)
Aneurysm
Diagnosis and Evaluation
Physical Examination and History
Symptoms
Hormonal symptoms often include growth arrest (especially in younger children, and especially with Cushing’s disease—oversecretion of ACTH), pubertal delay (including amenorrhea and menstrual irregularity which can be due to either primary hypogonadism or secondary to hyperprolactinemia), and galactorrhea (prolactinoma). Cushing’s disease can result in obesity, hirsutism, fatigue, and acne.
Headache is variable in patients, but an association with RCC has been reported .
Visual loss is often a bitemporal hemianopsia, although acute, severe loss of all vision can occur in the extremely rare entity of apoplexy [12].
Diabetes insipidus (DI) is extremely rare (except in the setting of nongerminomatous germ cell tumors. )
Prolactinoma—pubertal delay, menstrual irregularities, galactorrhea, gynecomastia
ACTH-secreting (Cushing’s disease)—obesity, growth delay, menstrual irregularities, acne, hypertension (and rare psychiatric issues)
GH-secreting—acromegaly, hypertension, gigantism (may be tall if prior to bone plate fusion, otherwise may have acromegalic facies and stature)
Patterns of Evolution
Nearly all symptoms are subacute to chronic, presenting over a period of months to years.
Apoplexy, however, can present over minutes to hours with extreme headache, vision loss, extraocular motor palsies and—in some cases—unconsciousness. However, apoplexy is vanishingly rare in children [12].
Evaluation at Presentation
Visual fields and a dilated fundoscopic examination can be useful to assess for compression of the optic chiasm.
Imaging and laboratory studies (see below).
Consider referral to endocrinology.
Laboratory Data
Endocrine panel—serum prolactin (PRL), cortisol, ACTH, insulin-like growth factor-1 (IGF-1), lutenizing hormone (LH), follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), free T4, GH, glucose, sodium, alpha-feto protein (AFP), and quantitative human chorionic gonadotrophin (hCG). Urine 24 h cortisol levels should be evaluated as well.
In rare cases, inferior petrosal sinus sampling with transvenous catheterization can be useful to attempt to identify and localize ACTH-secreting tumors. However, this is a difficult technique and generally should be reserved for select cases .
Decadron can be used to perform high- and low-dose cortisol suppression testing to distinguish between central (Cushing’s disease) and peripheral (ectopic) sources of elevated cortisol. The administration of low-dose decadron will not suppress adenoma-related hypercortisolemia, but high doses will suppress pituitary-related hypercortisolemia (but will not suppress ectopic (nonpituitary) cortisol sources).
Glucose testing can be done to detect the presence of a GH secreting tumor. Oral glucose is administered and serum GH levels checked 1–2 h afterwards. In healthy individuals, there is a normal suppression of GH levels to less than 5 ng/ml. In children with GH-secreting tumors, the levels will remain above 5 ng/ml and may actually increase to > 10 ng/ml.
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