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Abstract: Case Reports |

INTRACRANIAL HYPERTENSION CAUSED BY OBSTRUCTIVE SLEEP APNEA AND OBESITY HYPOVENTILATION SYNDROME FREE TO VIEW

Christine H. Won, MD, MS*; Carl Kirsch, MD
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Stanford University Medical Center, Stanford, CA



Chest. 2006;130(4_MeetingAbstracts):345S-b-346S. doi:10.1378/chest.130.4_MeetingAbstracts.345S-b
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INTRODUCTION: This report describes a case of papilledema and intracranial hypertension caused by obstructive sleep apnea (OSA) and obesity-hypoventilation syndrome (OHVS).

CASE PRESENTATION: A 23-year-old morbidly obese man presented to the emergency room with 4 months of headaches and progressive bilateral constrictive peripheral visual field loss. Fundoscopic exam revealed moderate bilateral papilledema. Intraocular pressure in each eye measured 23 millimeters of mercury (mmHg). A lumbar puncture showed an elevated opening pressure of 38 mmHg. Cerebral spinal fluid (CSF) studies and magnetic resonance imaging of the brain were normal. The patient was diagnosed with idiopathic intracranial hypertension (IIH). He was started on acetazolamide, and underwent 5 therapeutic lumbar punctures to remove a total of 250 milliliters of CSF. The patient showed no clinical improvement and he was referred for a ventriculo-peritoneal CSF shunt. During his hospital stay, the patient was noted to be chronically hypoxic with a pulse oximetry of 88%. His hematocrit was elevated to 61%. His serum bicarbonate level was 28 millimoles per liter. An arterial blood gas (ABG) while breathing air showed a pH of 7.29, pCO2 54 mmHg, and pO2 58 mmHg. The patient revealed a long history of loud snoring and excessive daytime somnolence. A nocturnal polysomnography confirmed severe OSA, with 118 apneic and hypopneic events per hour, and a pulse oximetry nadir of 55%. The patient was started on nocturnal noninvasive mechanical ventilation with supplemental oxygen for OSA and OHVS. Two days later, the patient reported improvement in his vision and headaches. His ABG improved to pH 7.31, pCO2 43 mmHg, and pO2 80 mmHg. The lumbar puncture opening pressure decreased to 26 mmHg. The CSF shunting procedure was deferred and the patient was discharged from the hospital on nocturnal noninvasive mechanical ventilation.

DISCUSSIONS: Idiopathic intracranial hypertension is defined as elevated intracranial pressure without ventriculomegaly or mass lesion, and with normal CSF composition. For unknown reasons, obesity is a major risk factor for IIH. Medications and invasive procedures that reduce or divert CSF help ameliorate symptoms, but weight loss is often the definitive treatment. Our case suggests a mechanism by which obesity may lead to intracranial hypertension. Obesity is a risk factor for OSA and OHVS. Respiratory sequelae of these syndromes include hypercapnea and hypoxemia. Chronic hypercapnea may precipitate elevated intracranial pressures by cerebral vasodilatation and greater CSF production, while hypoxemia may increase cerebral blood flow. In OSA, intermittent increases in intracranial pressure have been demonstrated during apneic episodes, with the degree of hypertension correlating with the duration of apnea and drop in peripheral blood oxygen saturation. [1] Acetazolamide may relieve intracranial hypertension not only by directly reducing CSF production, but also by creating a metabolic acidosis that stimulates ventilatory drive.

CONCLUSION: This patient's increased intracranial pressure was likely caused by OSA and OHVS, as evidenced by his rapid response to noninvasive mechanical ventilation. OSA and OHVS should be considered in the differential diagnosis of papilledema or raised intracranial pressure, particularly in the setting of hypoxemia and hypercapnea. A thorough sleep history and work-up should be obtained in these patients because treating the underlying cause may be more effective than traditional therapies for IIH.

DISCLOSURE: Christine Won, None.

Wednesday, October 25, 2006

2:00 PM - 3:30 PM

References

Jennum and SE Borgesen. Intracranial pressure and obstructive sleep apnea.Chest95(1989), pp.279–283. [CrossRef]
 

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References

Jennum and SE Borgesen. Intracranial pressure and obstructive sleep apnea.Chest95(1989), pp.279–283. [CrossRef]
 
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