Bariatric Times

MAR 2017

A peer-reviewed, evidence-based journal that promotes clinical development and metabolic insights in total bariatric patient care for the healthcare professional

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17 The Medical Student Notebook Bariatric Times • March 2017 positional changes), photopsia and d iplopia, as well as possible permanent visual loss. 24 While headache was the single most commonly reported symptom, headache timing, quality, and s everity may be highly variable in patients with IIH. For example, many patients reported constant or daily headaches while others reported only intermittent h eadaches and the median number of days per month with headache was found to be 12, with a range from 1 to 30. Similarly, patient descriptions of visual disturbances a nd tinnitus as well as other symptoms may vary significantly .17, 25 Thus, patients with some constellation of the above symptoms may be suspected of IIH i n the appropriate clinical and epidemiological setting, but these symptoms are rarely specific for a diagnosis of IIH and other causes of intracranial hypertension must also b e considered. On physical exam, one of the most common findings in patients with IIH is papilledema, a condition in which increased pressure in or around the brain causes the part of the optic nerve inside the eye to swell. While it is generally bilateral and symmetric, unilateral or asymmetric papilledema may also be noted. 26 –28 In addition to offering diagnostic information, the finding of papilledema is also of prognostic value as patients with more severe papilledema have been shown to be at higher risk of permanent visual loss and patients without papilledema are at lower risk for loss of vision. 2 7, 29-31 Thus, evaluation for visual loss, which is perhaps the most important cause of morbidity in IIH, is a critical component of assessing patients with IIH. Visual loss in IIH may manifest as decreased visual acuity as well as visual field loss (particularly of peripheral vision although the physiological blind spot may also be pathologically enlarged). The latter is considered to be a somewhat more sensitive indicator of visual loss in IIH at the time of presentation. 24, 32, 33 Various studies have suggested that anywhere from 6 to 24 percent of patients may develop severe visual impairment or blindness. 34–37 The typical course of untreated IIH consists of chronic symptoms lasting months to years with gradual symptomatic progression over time. However, there is a subset of patients who present with a more rapidly progressive course leading to permanent visual loss within weeks of onset. 38–41 The visual loss observed in IIH is thought to be caused by axoplasmic stasis within the optic nerve. Transmission of increased intracranial pressure causes increased pressure of the optic n erve within its intracranial sheath, and thus the axons traveling within the intracranial portion of the optic nerve experience a much higher pressure than the cell bodies l ocated within the globe because IIH does not increase the pressure within the globe. This difference in pressure along the course of the neurons interferes with normal a xonal transport thereby causing axoplasmic stasis, which underlies the development of both papilledema and visual loss in patients with IIH. 42–44 PATHOPHYSIOLOGY OF IIH As its name suggests, the pathophysiology of IIH is not entirely understood. Several m echanisms have been proposed to explain the development of IIH and to attempt to account for the increased incidence in patients with obesity, particularly women of c hildbearing age (Figure 1). The most commonly cited proposed mechanism for pathogenesis of IIH relates to development of intracranial venous hypertension, as p atients with IIH have a similar clinical presentation to patients with conditions such as cerebral venous thrombosis and other causes of obstructed venous outflow. S everal reports have described cerebral venous outflow abnormalities on magnetic resonance venography (MRV) in patients diagnosed with IIH, a lthough the frequency and implications of these findings have been controversial. 45–47 In one case- control study, 29 patients diagnosed

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