Case of the Month
Section Editor: Nicholas Stence, MD
Children's Hospital Colorado, Aurora, CO
May 2017
Next Case of the Month coming June 6...
Basal Ganglia Germinoma
- Background:
- Central diabetes insipidus is a known presentation of intracranial germ cell tumors (as well as other entities) that can involve the infundibulum and disrupt transport of ADH and oxytocin from the hypothalamus to the neurohypophysis (posterior pituitary gland).
- Absence of the normal posterior pituitary bright spot may be seen in these patients, and this entity should be followed with surveillance imaging to assess for the development of a mass lesion.
- This case is unique in that this patient was followed to evaluate for suspected tumor development, which was thought to be a possibility in the suprasellar/infundibular region; however, a basal ganglia germinoma ultimately developed.
- Germinomas most commonly occur near the midline and predominantly involve the pineal and suprasellar regions. The third most common location of CNS germinomas is within the basal ganglia and thalami (~10%).
- Clinical Presentation:
- Basal ganglia germinomas most commonly present with progressive hemiparesis.
- Germinomas in the sellar/suprasellar regions can present with symptoms of diabetes insipidus (polydipsia and increased frequency of micturition), as well as other hypothalamic pituitary axis dysfunction.
- Key Diagnostic Features:
- Absence of the normal posterior pituitary bright spot may be nonpathologic in the adult population (thought to be due to variations in the protein content of the neurosecretory granules of ADH and oxytocin); however, absence of the bright spot in children should be viewed as abnormal, and serial imaging should be performed to evaluate for development of an infundibular mass, especially in the setting of a patient with DI.
- Basal ganglia/thalamic germinomas can initially present with hypointense signal on SWI, secondary to intratumoral hemorrhage or mineralization. T2/FLAIR hyperintense signal eventually develops and may not initially enhance. Ultimately, enhancement is the rule. These tumors may be unilateral or bilateral.
- Atrophy of ipsilateral cerebral peduncle or cerebral hemisphere may be seen.
- Basal ganglia germinomas do not commonly demonstrate the increased attenuation on CT and diffusion restriction on MRI that are seen in pineal region and infundibular germinomas.
- Differential Diagnoses:
- Absence of the normal posterior pituitary bright spot in a child:
- germinoma, LCH, lymphoma/leukemia, mets
- Enhancing basal ganglia mass in a child:
- hypothalamic or optic pathway glioma, germinoma, lymphoma, encephalitis
- Absence of the normal posterior pituitary bright spot in a child:
- Treatment:
- Chemotherapy and radiation therapy are first-line treatments (as they are for germinomas in other locations), with good overall prognosis.
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