Continuous Glucose Monitors Detect Nocturnal Hypoglycemia Before Seizures

"Concerns over nocturnal hypoglycemia are a major reason for people with type 1 diabetes welcoming the possibility of using real-time continuous glucose monitoring (CGM) with real-time hypoglycemic alarms," Dr. Bruce Buckingham of Stanford University, California, and colleagues write.

However, they note, subcutaneous CGM has a 5- to 18-minute delay when compared with glucose levels measured directly from the blood. Greater delays occur when blood glucose levels are rapidly changing. This might mean that a seizure could occur before an alarm sounds, although there are no published reports of nocturnal hypoglycemic seizures while a patient is wearing a CGM device.

In the current study, the researchers examined the duration of sensor-detected nocturnal hypoglycemia preceding a hypoglycemic seizure by asking investigators from around the world to submit cases. Four were included in the study.
The four patients had sensor hypoglycemia levels less than 60 mg/dL. Nocturnal hypoglycemia was documented on the CGM record for 2.25 to 4 hours before the seizure occurred.

In two cases, the monitors were early models without alarms, but in one instance the alarm was inaudible under the subject's bedding.

"Glucose sensors should have sufficiently robust alarm systems, particularly at night, to insure either the patient or a surrogate is awoken to intervene," Dr. Buckingham and colleagues emphasize. "We suggest augmenting the alarm with a bedside device that would turn on a light and transmit the alarm to another location in the house, such as a parent's bedroom."

Diabetes Care 2008; 31:2110-2112.