A group led by the Department of Neurosurgery at the Brain Research Institute, Niigata University, has successfully treated a patient with a brainstem glioma harboring a rare IDH2 mutation. The case report was published online in the journal Frontiers in Oncology.

The patient initially presented with a gradual loss of hearing in the left ear, and MRI showed a lesion at the left side of the brainstem, near the root exit zone of the left acoustic nerve.

Initially, a brainstem glioma with H3K27M mutation was suspected. However, the gradual clinical course and unusual location of the brainstem glioma were considered atypical.

The patient underwent magnetic resonance spectroscopy in which 2-hydroxyglutarate, a marker for IDH mutation, was evident. Subsequently, the patient underwent a surgical biopsy, and pathological analysis revealed a rare IDH2 mutation.

Although most brainstem gliomas with H3K27M mutation have an unmethylated MGMT promoter and thus are resistant to temozolomide, about 70% of IDH-mutant astrocytomas are known to have a methylated MGMT promoter and are sensitive to temozolomide.

A team led by Dr. Manabu Natsumeda successfully treated the patient with temozolomide and radiation, and the tumor dramatically shrank, and surprisingly, the patient’s hearing improved. The patient has been off treatment after one year of maintenance temozolomide treatment, but the tumor has not relapsed.

“We were fortunate to detect IDH mutation in this patient, or else we would not have used temozolomide. This case illustrates the importance of screening by MRS for IDH mutation and a safe biopsy to determine the optimal treatment,” explains Dr. Natsumeda.