(847) 378-0517 or bvd@aans.org
EMBARGOED FOR RELEASE ON APRIL 18
NEW ORLEANS (April 18, 2005) Traumatic brain injury (TBI) is a substantial cause of mortality in the United States. Gender has often been overlooked as a factor affecting outcome after TBI. This may be because the majority of TBI patients under the age of 65 are male. TBI in younger patients is usually caused by trauma, violence, and accidents. In patients 65 and older, TBI is usually attributed to falls and motor vehicle accidents, which may result from motor, sensory, and cognitive decline. In older patients, the gender distribution of cases is more balanced.
Research has shown physiologic differences in cerebral blood flow (CBF) between males and females, but the effect of gender on outcome after TBI has not been extensively studied. Researchers examined gender and age in TBI patients in the study Age-related Changes in Cerebral Blood Flow May Explain Worse Outcome in Female Head Trauma Patients, which will be presented by Deborah M. Lee, BA,
3:00 to 3:15 p.m. on Monday, April 18, 2005, during the 73rd Annual Meeting of the American Association of Neurological Surgeons in New Orleans. Co-authors are Thomas C. Glenn, PhD,
W. John Boscardin, PhD, Jean F. Soustiel, MD, and Neil A. Martin, MD.
A total of 90 male and 26 female patients were studied, with 34 controls for the purpose of comparing metabolic parameters (e.g., lactate, glucose, oxygen levels) between head trauma patients and normal subjects. Patients were from two institutions, UCLA Hospital in Los Angeles, Calif., and Rambam Hospital in Haifa, Israel. Eligible TBI patients included all mechanically ventilated patients with moderate or severe head injury, age 14 and older, who were admitted to the hospital within 24 hours of injury. Moderate or severe head injury was defined as closed or penetrating injury with post-resuscitation Glasgow Coma Scale score (GCS) less than or equal to 13. Individuals with terminal illnesses, severe neurological illnesses (Parkinson's, Alzheimer's), or acute complete spinal cord injury were excluded.
The 133-Xenon technique was used to measure CBF in patients at UCLA Hospital. In this method, 133-Xenon is administered to the patient, and cerebral clearance is measured with a band of probes placed around the patient's head. A computer calculates the rate of 133-Xenon clearance in the brain, and thus gets a measurement of CBF. The dual-beam Doppler technique was used to measure CBF in patients at Rambam Hospital. In this method, CBF is calculated using an ultrasound device placed on the head. Studies were scheduled for every 12 hours for the first 48 hours after injury (postinjury days 0 and 1) and then daily on postinjury days 2, 3, 4, 5, 7, and 9.
Neurological outcome was assessed six months after injury with the 5-point Glasgow Outcome Scale (GOS) by investigators blinded to the patients' metabolic and other clinical data. For the assessment of redictors of outcome, the GOS was used as both a linear scale (1 = death to 5 = good recovery) and as a dichotomized outcome score of favorable (GOS 4 or 5, indicating good recovery or moderate disability) versus unfavorable (GOS 1, 2, or 3, indicating severe disability, vegetative state, or death).
In both genders, there was a trend of decreasing CBF and GOS with increasing age. Compared to males, females showed a much steeper decline in both CBF and GOS as they aged. In females, the trend of decreasing CBF with increasing age reached significance between the youngest (<25 years) and oldest (60+) age groups. Mean GOS scores followed a similar trend: the youngest age group had a mean GOS of 3.9, and the oldest age group had a mean GOS of 1.6. In males, CBF and GOS also decreased with increasing age, but these patterns did not reach statistical significance. "It appears that the association of age and outcome may be partially explained by the changes in CBF that occur with age," stated
Deborah Lee.
Dichotomized GOS scores were also used, with GOS of 4 or 5 indicating a favorable outcome versus GOS of 1, 2, or 3 indicating an unfavorable outcome. Females with good outcome (GOS 4 or 5) had much higher CBF than females with poor outcome (GOS 1, 2, 3). In contrast, males with good outcome had only slightly higher CBF than males with poor outcome.
The difference in CBF between females with good outcome and those with poor outcome was greater than the corresponding difference between male patients with good or poor outcome. "In this study, outcome and CBF values decreased with increasing age in both males and females, but this decrease was more extreme in females. This suggests that increasing age may affect female trauma patients more adversely than it does males, and that CBF is a stronger predictor of outcome in females than in males," remarked Lee.
One possible explanation of the greater decrease in CBF with increasing age in female patients is the loss of female hormones with aging. Numerous animal studies have demonstrated the protective effects of estrogen and progesterone in the brain. After experimental head injury, animals with female sex hormones maintained higher brain perfusion than male animals. Sex hormones are lost more abruptly in human females, due to menopause, than they are in males which may explain differences in CBF between male and female head trauma patients as they age.
"While the majority of TBI patients age 65 and younger are male, some studies indicate a predominance of female TBI patients in the 70+ age group, which is one reason additional studies in this area are crucial to further clarify the effect of gender on the physiology of TBI," concluded Lee.
Founded in 1931 as the Harvey Cushing Society, the American Association of Neurological Surgeons (AANS) is a scientific and educational association with more than 6,800 members worldwide. The AANS is dedicated to advancing the specialty of neurological surgery in order to provide the highest quality of neurosurgical care to the public. All active members of the AANS are certified by the American Board of Neurological Surgery, the Royal College of Physicians and Surgeons (Neurosurgery) of Canada or the Mexican Council of Neurological Surgery, AC. Neurological surgery is the medical specialty concerned with the prevention, diagnosis, treatment and rehabilitation of disorders that affect the entire nervous system, including the spinal column, spinal cord, brain and peripheral nerves.
