The Use of Hyperventilation in Contrast-Enhanced MR Imaging of Brain Tumors

Pronin et al investigated the use of hyperventilation in contrast-enhanced MR imaging of brain tumors as an inexpensive and safe method to increase sensitivity for visualizing brain tumors (1). They mentioned the importance of determining the safety of hyperventilation, which occasionally causes seizures. Although we agree with the safety of hyperventilation in general, we recently saw a rare complication of hyperventilation.

A 74-year-old right-handed man, who had a history of migraine headaches with aura for 20 years, was hospitalized. Two years previously Desyrel was prescribed for him (100 mg at bedtime). Prior to admittance, he complained of a 1-week course of intermittent right hemihypesthesia and aphasia (anomia with semantic paraphasia), culminating in intermittent episodes of right hemiparesis that lasted minutes. During hospitalization, he was treated with low-molecular-weight Heparin and his usual daily 5 grains of aspirin, and his symptoms resolved.

During his EEG, after 2 minutes of hyperventilation, he developed frontal intermittent rhythmic activity of 70 uv 2 Hz Δ, accompanied by right hemiparesis and aphasia. For 2 seconds, there was intermittent diffuse bilateral activity of 40 uv 3 Hz Δ, then an acceleration to 35 uv 5–6 Hz 𝛉, which disappeared when his right hemiparesis and aphasia subsided (Fig).

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A CT scan showed a 4-cm left parietal decreased density with mild mass effect flattening the wall of the lateral ventricle. On an MR scan, this area was hypointense on T1-weighted images and hyperintense on T2-weighted images, enhancing with contrast material. Biopsy of this mass showed a glioblastoma multiforme.

Ross (2) described transient tumor attacks in 1983, which was followed by a related large multicenter trial in 1993 (3) and a review of four cases by Cameron 1994 (4). One of Cameron's four cases of meningioma yielded an EEG showing “bursts of …activity below 8 Hz in the …midtemporal region …consistent with a slowly growing neoplasm.”

Shregel et al (5) and Pronin et al (1, 6) have demonstrated that there is decreased autoregulation and CO₂ sensitivity or, paradoxically, increased blood flow within brain tumors with hyperventilation. If hyperventilation can lead to paradoxically increased blood flow within a tumor, but normal physiologic decreased blood flow in the normal brain around a tumor, it may lead to relatively more tumor mass effect. This would rarely result in focal neurologic signs and EEG slowing that could be reversed by stopping hyperventilation.