The story began when the patient was thirteen years old. She visited a local clinic complaining of fatigue and fever, and routine laboratory tests revealed two red flags that pointed away from an ordinary infection: hypothyroidism and abnormally elevated sodium levels in her blood, a condition known as hypernatremia. Both findings suggested a problem with the pituitary gland and the hormonal circuitry it controls. A cranial computed tomography scan then identified a mass in the suprasellar region, the anatomical neighborhood just above the pituitary where the optic chiasm, pituitary stalk, and hypothalamus are packed closely together. She was referred to a pediatric department for further evaluation.

Because the mass sat in a location where surgical biopsy carried a high risk of injuring surrounding brain structures, the medical team did not attempt to obtain tissue for histological examination. Instead, they relied on indirect evidence. Magnetic resonance imaging showed a suprasellar mass extending toward the third ventricle and the pineal region, involving the hypothalamus itself. In addition, the patient’s serum level of beta-human chorionic gonadotropin, a hormone sometimes secreted by certain germ cell tumors, was mildly elevated at 0.3 nanograms per milliliter. Taken together, the imaging findings and the tumor marker were sufficient for a clinical diagnosis of primary intracranial germinoma, a rare germ cell tumor that arises in the midline of the brain and is particularly common in children and adolescents. At the time of diagnosis, she already had panhypopituitarism, meaning near-total loss of pituitary hormone production, and central diabetes insipidus, a condition in which the brain fails to produce the hormone that allows the kidneys to conserve water.

Treatment followed a standard strategy for intracranial germinoma: chemotherapy using the CARE regimen, followed by whole-ventricular irradiation at a total dose of 23.4 Gy delivered in thirteen fractions. The response was excellent. Follow-up magnetic resonance imaging demonstrated marked tumor regression, and the beta-human chorionic gonadotropin level normalized to 0.1 nanograms per milliliter or below. Yet even before treatment, the tumor’s location had already left its signature on her thermoregulation. She suffered persistent hyperthermia, with body temperatures ranging from 37 to 38 degrees Celsius, despite the absence of any clinical or laboratory evidence of infection or inflammation. The team suspected that the tumor’s infiltration of the hypothalamus had disrupted the brain’s thermostat. Roughly one month after therapy ended, her temperature settled into a normal range of 36 to 37 degrees, and for several years she remained clinically stable, with only occasional mild temperature elevations during summer months.

The first sign that something deeper was wrong arrived eight years after the original diagnosis, when the patient was twenty-one. In February of that year, she presented with fatigue, abdominal pain, and poor oral intake. Laboratory tests revealed hyponatremia, a dangerously low blood sodium level of 131 milliequivalents per liter, along with hypoglycemia, a blood glucose of 66 milligrams per deciliter. Her body temperature on arrival was 34.5 degrees Celsius, well below the threshold of clinical hypothermia. Physicians initially interpreted the picture as a sick-day state triggering relative adrenal insufficiency, and they administered stress-dose steroids while admitting her for active external warming. Her symptoms improved and she was discharged after seven days. Notably, however, the serum cortisol level drawn at presentation, which became available only later, was actually elevated at 56.2 micrograms per deciliter, a detail that would prove important.

A year later, the pattern repeated with greater severity. In January, at twenty-two years of age, she arrived with fatigue and was found to be profoundly hypothermic at 33.3 degrees Celsius with a bradycardic heart rate of just 41 beats per minute. In March of the same year she was readmitted with fatigue and decreased responsiveness, her temperature at 35.2 degrees. Once again, stress-dose steroids failed to produce rapid improvement, and once again the later cortisol measurement came back elevated, this time at 42.1 micrograms per deciliter. Brain magnetic resonance imaging showed no tumor recurrence and no new lesions. Hypothermia in the 34-degree range persisted throughout her hospitalization, but with active external warming her general condition gradually recovered, and she was discharged on the eleventh day.

The clinical reasoning that followed is what makes this case instructive. Adrenal crisis, the most feared endocrine emergency in patients with pituitary dysfunction, was initially suspected during both hypothermic episodes. But two observations argued against it: the cortisol levels measured during the episodes were elevated rather than low, and steroid supplementation did not rapidly resolve the symptoms. Combined with the absence of tumor recurrence on imaging, these findings pointed the team toward a different diagnosis: delayed hypothalamic dysfunction, a recognized late complication of cranial radiotherapy that can emerge months to decades after treatment in a dose- and time-dependent manner. The hypothalamus, the report’s authors emphasize, is more radiosensitive than the pituitary gland and may suffer functional impairment even at relatively low radiation doses. The whole-ventricular irradiation this patient received at 23.4 Gy may therefore have contributed to the slow, delayed failure of her brain’s temperature control system.

The metabolic derangements that accompanied her hypothermic episodes also fit this explanation. Hyponatremia and hypoglycemia during such episodes are more plausibly attributable to hypothermia itself than to adrenal failure. Severe cold impairs hepatic gluconeogenesis, the liver’s production of glucose, and blunts the counterregulatory hormonal responses, including glucagon release and sympathetic nervous system activation, that normally defend blood sugar and blood pressure against stress. Reduced oral intake compounds the problem. In other words, the hypothermia was not merely a symptom; it was the primary engine of her clinical deterioration and impaired consciousness, driving the laboratory abnormalities that had initially misled her physicians toward a diagnosis of adrenal insufficiency.

What can be done for a patient whose internal thermostat has failed? The report notes that several pharmacological agents targeting neurotransmitter systems have shown benefit in select cases of hypothermia associated with hypothalamic dysfunction, but no established therapy exists and the supporting evidence remains limited. Active external warming therefore constitutes the mainstay of management, encompassing direct measures such as electric blankets and hot water bottles as well as environmental temperature control with heating devices. Acting on this understanding, the medical team recommended proactive thermal management during the winters when the patient was twenty-three and twenty-four: maintaining room temperature above 20 degrees Celsius, using an electric blanket, and consuming warm beverages as part of daily life. Since these measures were implemented, she has experienced no further episodes of clinical deterioration or decreased consciousness requiring hospitalization, a strikingly simple intervention with apparently decisive results.

The broader lesson of this case extends well beyond one patient. Intracranial germinomas are cured in the great majority of cases, and long-term survival is the expected outcome. But as childhood and adolescent brain tumor survivors live decades beyond their treatment, the late effects of therapy become the dominant medical challenge. Endocrine surveillance for growth hormone deficiency, hypogonadism, and adrenal insufficiency is standard practice, yet thermoregulatory capacity is rarely assessed systematically. This report suggests it should be. A hypothalamic thermostat damaged by tumor infiltration or by radiation may compensate quietly for years before failing, and the failure mode, recurrent profound hypothermia masquerading as adrenal crisis or sepsis, is easy to misdiagnose. For clinicians caring for long-term survivors of suprasellar and hypothalamic tumors, the message is concrete: follow-up should address not only endocrine function but also thermoregulatory function, and practical lifestyle guidance about cold exposure may prevent life-threatening complications years after apparently successful treatment. In an era when cancer survival is increasingly measured in decades, the hypothalamus, that small almond-shaped guardian of the body’s internal climate, deserves a permanent place on the list of structures to watch.

Subject of Research: Delayed hypothalamic thermoregulatory dysfunction causing recurrent hypothermia after treatment of a suprasellar germinoma

Article Title: Delayed Hypothalamic Dysfunction Presenting as Recurrent Hypothermia After Treatment of Suprasellar Germinoma: A Case Report

Article References: Nishimura, A., Kado, T., Fujisaka, S., Kato, M., & Ishiki, M. (2026). Delayed Hypothalamic Dysfunction Presenting as Recurrent Hypothermia After Treatment of Suprasellar Germinoma: A Case Report. Clinical Case Reports, 14(10), Article e73535. https://doi.org/10.1002/ccr3.73535

Image Credits: AI Generated

DOI: 10.1002/ccr3.73535

Keywords: hypothalamus, hypothermia, suprasellar germinoma, cranial radiotherapy, thermoregulation, late complications, pituitary dysfunction, brain tumor survivorship, cortisol, case report, endocrinology, radiation therapy

For decades, descriptive studies have suggested that these radiation-induced tumors behave worse than their sporadic counterparts. They appear to present at younger ages, more often as multiple synchronous lesions, with a higher share of atypical WHO grade 2 histology, and with higher recurrence rates after surgery. The problem with those earlier comparisons, however, is that they were largely unmatched. Radiation-exposed patients and historical sporadic controls differed systematically in age, tumor grade, and extent of surgical resection, all of which independently influence the odds of a tumor coming back. Without controlling for those factors, no one could say whether the worse outcomes reflected an intrinsically more aggressive tumor biology or simply a skewed comparison.

A new study from the University Medical Center Mainz in Germany, published in the Journal of Neuro-Oncology, set out to answer that question with a methodological upgrade. Led by neurosurgeons Leon Schmidt and Dragan Jankovic, with Darius Kalasauskas as senior author, the team identified every radiation-induced intracranial meningioma resected at their institution between 2007 and 2023, then applied propensity score matching to construct a fair comparison group. To qualify as radiation-induced, tumors had to satisfy Cahan’s criteria, the classic set of conditions used for radiation-associated second cancers: the tumor had to arise within a previously irradiated field, at least five years had to have elapsed since irradiation, the meningioma diagnosis had to be histologically confirmed, and the tumor could not have been present at the time of the original treatment.

From an initial pool of 817 eligible historical sporadic cases, the researchers matched 195 controls to 39 radiation-induced meningioma patients at a one-to-five ratio, balancing the groups on age, WHO grade, and Simpson grade, the standard measure of how completely a meningioma has been resected. Propensity scores were calculated with a logistic regression model, and nearest-neighbor matching without replacement was performed using a caliper width of 0.2 standard deviations of the logit of the score. After matching, standardized mean differences confirmed that the groups were well balanced on the key prognostic factors, with most values falling below the conventional threshold of 0.10, though some residual imbalance remained for certain Simpson grade levels.

The results were striking. Even after this careful balancing, radiation-induced meningiomas recurred significantly more often than matched sporadic tumors: 28 percent versus 17 percent, a difference that reached statistical significance. Median progression-free survival, the time from surgery to the first radiographically documented recurrence or progression, was 66 months in the radiation-induced group compared with 88 months in controls. In total, 44 relapse events were observed across the matched cohort, 11 among the 39 radiation-exposed patients and 33 among the 195 controls.

The most rigorous test came from multivariable Cox proportional hazards regression, which adjusted simultaneously for complete resection and for surgically complex tumor location. In that model, radiation-induced tumor status remained an independent predictor of shorter progression-free survival, with a hazard ratio of 2.1, meaning the exposed tumors carried roughly twice the risk of relapse at any given time. Complete resection, defined as Simpson grade I or II, was strongly protective, cutting the hazard of recurrence to about 0.29 of that seen after incomplete removal. Surgically complex location, by contrast, did not achieve a significant association. The proportional hazards assumption was verified using Schoenfeld residuals and was not violated for any covariate.

Yet the study is notable as much for its caution as for its findings. The authors emphasize that matching did not erase every clinically relevant difference between the groups. Radiation-induced patients carried a higher comorbidity burden, measured by the Charlson Comorbidity Index, with a median score of 2 versus 0 in controls. Nearly 39 percent of them had undergone prior cranial surgery, compared with just over 4 percent of controls, likely reflecting interventions related to the original condition for which they were irradiated. Their preoperative Karnofsky Performance Status was modestly lower, and adjuvant radiotherapy after meningioma resection was administered far more often in the exposed group, 33.3 percent versus 11.3 percent. Because these variables were not included in the propensity score model, residual measured and unmeasured confounding cannot be excluded, and the authors explicitly warn that the results should not be interpreted as evidence of intrinsically more aggressive tumor biology.

The biological question remains open. Previous work has suggested that therapeutic radiation drives distinct molecular changes in meningiomas, including radiation-induced DNA damage, chromosomal instability, and structural aberrations of the NF2 gene, a key tumor suppressor frequently altered in these tumors. A 2017 study in Nature Communications showed that radiation for childhood cancer can produce structural rearrangements of NF2 specifically in radiation-associated meningiomas, and other groups have reported epigenetic signatures such as loss of H3K27me3. But molecular data were not systematically available in the Mainz cohort, so the study cannot determine whether the earlier relapses reflect these biological differences or the lingering effects of confounding. The authors call for further molecular studies to settle the question.

The limitations of the work are worth taking seriously. It is a retrospective, single-center analysis with only 39 radiation-induced cases, which limits statistical power, and the median follow-up of 20 months is short for a tumor whose late recurrences beyond five years are well described. Follow-up duration also differed between groups, with longer surveillance in the radiation-induced patients, and differences in imaging frequency between the two populations cannot be ruled out in a retrospective design. Historical pathology specimens were not systematically rereviewed under the 2021 WHO classification, so some degree of grade misclassification in older cases is possible. The authors also note that because Simpson grade was included as a matching covariate, the similar rates of complete resection between groups, 71.8 percent versus 76.4 percent, are expected by design and should not be read as evidence of comparable resectability.

Still, the methodological contribution is real. By applying propensity score matching to this question for the first time, the Mainz team has strengthened and refined an association that earlier unmatched studies had only suggested, showing that radiation-induced meningioma status predicts earlier relapse even when age, grade, and extent of resection are held constant. The practical messages for clinicians are twofold. First, patients with a history of cranial irradiation deserve long-term surveillance, since their tumors may return sooner after surgery. Second, complete surgical resection remains the single most powerful modifiable predictor of progression-free survival, supporting maximal safe resection whenever clinically feasible. As the ranks of childhood cancer survivors continue to swell, understanding and managing these delayed consequences of life-saving radiation will only become more important.

Subject of Research: Recurrence risk and progression-free survival of radiation-induced cranial meningiomas compared with sporadic meningiomas using propensity score matching

Article Title: Radiation-induced cranial meningiomas are associated with earlier relapse: a propensity score–matched cohort study

Article References: Schmidt, L., Jankovic, D., Thavarajasingam, S., Fakak, R., Kosterhon, M., Dauth, A., Brockmann, M., Sommer, C., Ringel, F., & Kalasauskas, D. (2026). Radiation-induced cranial meningiomas are associated with earlier relapse: a propensity score–matched cohort study. Journal of Neuro-Oncology, 179(3), Article 97. https://doi.org/10.1007/s11060-026-05809-8

Image Credits: AI Generated

DOI: 10.1007/s11060-026-05809-8

Keywords: radiation-induced meningioma, meningioma recurrence, propensity score matching, progression-free survival, extent of resection, cranial radiotherapy, WHO grade, Simpson grade, neurosurgery, brain tumors, NF2, ionizing radiation