The relationship between intracranial pressure and obesity: an ultrasonographic evaluation of the optic nerve.

BACKGROUND: Measurements of optic nerve sheath diameter (ONSD) with noninvasive ocular ultrasonography have been shown to be accurate in determining increased intracranial pressure. Obesity is associated with chronic increases in intraabdominal pressure that could consequently result in intracranial hypertension. By utilizing ONSD ultrasonographic measurements, we compare the difference that may exist between obese and non-obese patients.

STUDY DESIGN: We prospectively collected data from patients who underwent laparoscopic procedures in the supine position between July 2013 and March 2014. Ophthalmic pathology was not present in any patient. Ultrasonographic measurement of the ONSD was obtained sagittally with a 12-MHz transducer 3 mm from its origin. The measurements were taken at 0, 15, and 30 min, and at the end of surgery.

RESULTS: There were 62 subjects, 28 females (45.2 %) and 34 males (54.8 %), with a mean age of 44.22 ± 10.44 years (range 23-66). Forty-eight percent of patients were non-obese, and 52 % of patients were obese. The mean body mass index was 30.70 ± 7.61 kg/m(2) (range 20.0-59.5). The mean ONSD of non-obese and obese patients was 4.7 and 5.5 mm at baseline (p = 0.01), 5.4 and 6.2 mm at 15 min (p = 0.01), 5.8 and 6.6 mm at 30 min (p = 0.01), and 5.1 and 5.7 mm after deflation of pneumoperitoneum (p = 0.03), respectively.

CONCLUSIONS: Utilizing a noninvasive method to measure the ONSD, a chronic increase in intracranial pressure in obese patients was demonstrated. The increase in the ONSD during laparoscopic procedures reflects a temporary increase in the intracranial pressure from baseline.