A 16-year-old girl who presented with headache, nausea, irregular menstrual cycle, and galactorrhea was found to have hyperprolactinemia (blood prolactin level, 200 ng/mL; normal, < 20 ng/mL). The findings of the neurologic examination were normal, and no physical anomaly was detected. The peripheral blood hormone level including luteinizing hormone, follicle-stimulating hormone, antidiuretic hormone, and cortisol was normal, with the exception of the prolactin level, which was elevated.

On MR imaging of the sella, an enlarged empty sella turcica filled with cerebrospinal fluid was seen. A vertical canal extending from the floor of the sella turcica to the nasopharynx was detected. The pituitary gland was located inferiorly in this canal, and some portion of the gland extended into the nasopharynx (Fig. 1A). The anterior lobe of the pituitary gland was normal in size and signal intensity and showed a normal enhancement pattern on dynamic contrast-enhanced MR imaging. The normal hyperintensity of the neurohypophysis was not detected in the posterior pituitary lobe. The stalk was seen at the midline extending a long distance from the hypothalamus to the pituitary gland. The stalk was thin and tight, which we believe was the result of traction. The MR imaging findings were consistent with the large craniopharyngeal canal associated with the nasopharyngeal extension of the pituitary gland.

In addition to these findings, a 15 × 20 mm mass was noted at the region of the hypothalamus. On T1-weighted spin-echo and fast T2-weighted spin-echo images, the mass was isointense with brain parenchyma, had a lobulated and sharp contour, and had mass effect on the optic chiasm that was displaced anteriorly. The mass also showed no enhancement after contrast infusion. The MR imaging findings of the mass were consistent with hypothalamic hamartoma (Fig. 1B).

Unenhanced high-definition three-dimensional CT of the skull base was performed to better delineate the bony canal. On CT, a bony canal measuring 13 mm in diameter with smooth margins extending from the floor of the sella turcica to the nasopharynx was seen (Fig. 1C). No other bony anomaly was noted.

Because the pituitary gland did not have features suggestive of adenoma on MR imaging, we assumed that the hyperprolactinemia was caused by the traction of the pituitary stalk.

The term “craniopharyngeal canal” or “persistent hypophyseal canal” is generally used to describe a small and vertical midline defect in the skull base that measures less than 1.5 mm in diameter. Its incidence in adults has been reported as 0.42% [2]. Because of its small size, the craniopharyngeal canal is rarely seen on radiographs of the skull. The term craniopharyngeal canal is also used to describe a rarer and much larger bony canal in the same location. Currarino et al. [1] provided other names to describe this skull base defect, including the large craniopharyngeal canal and transsphenoidal canal, which differ from the craniopharyngeal canal or persistent hypophyseal canal by virtue of having a greater size and association with special craniofacial anomalies. It has also been suggested that the large craniopharyngeal canals or transsphenoidal canals are related not to the persistent craniopharyngeal canal but rather to transsphenoidal meningoencephalocele [4].

The etiology of the craniopharyngeal canal is unknown. There are two main theories regarding to the origin of the canal [1, 2]. One theory proposes that this canal is the remnant of the Rathke pouch. The other theory states that the canal represents the remnant of a vascular channel formed during osteogenesis.

The diagnosis in this case was a large craniopharyngeal canal (or transsphenoidal canal) associated with nasopharyngeal extension of the pituitary gland. A review of the literature revealed few other reported cases of the large craniopharyngeal canal associated with a nasopharyngeal mass that proved to be the pituitary gland [5, 7]. Most of these patients have undergone hypophysectomy because the diagnosis was unsuspected. Currarino et al. [1] have classified cases of large craniopharyngeal canal in those associated with nasopharyngeal masses and in those that are not associated with these masses. Nasopharyngeal masses mentioned in their series were either parts of the third ventricle and pituitary gland or a variety of meningoencephalocele. In addition, these authors noted a high prevalence of craniofacial anomalies associated with a large craniopharyngeal canal such as hypertelorism, midfacial cleft, cleft lip and palate, abnormal optic tracts, malformed eyes, and absence of corpus callosum [1]; none of these were present in our patient.

In summary, our patient had a large craniopharyngeal canal associated with a normally functioning nasopharyngeal pituitary gland. We presumed the elevated prolactin level to be due to traction on the pituitary stalk and that the hypothalamic hamartoma is an incidental finding. To our knowledge, no relationship between the elevated prolactin level and the hypothalamic hamartoma has been reported in the literature.

Address correspondence to G. Ekinci.