Idiopathic Intracranial Hypertension
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Idiopathic Intracranial Hypertension

Author: Logan University/Friday, January 08, 2016/Categories: August 2015

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A 26-YEAR-OLD FEMALE WITH LOW-BACK PAIN AND HISTORY OF MIGRAINE.

A 26-year-old female with a BMI of 26.7 was seen for complaints of low-back pain with cervical and thoracic spine stiffness. Two years prior, she had been diagnosed with classic migraine following headaches with aura. Several weeks before her visit, her headaches worsened and were accompanied by vertigo and visual disturbances. Seen in the emergency department with headache and reduced visual acuity, she was again given a diagnosis of chronic migraine. She consulted a PCP with no additional diagnosis, but following an evaluation by an optometrist, papilledema was detected. A diagnosis of idiopathic intracranial hypertension (IIH) was suggested. An MRI (see Fig. 1-3) of the brain with and without contrast was obtained and revealed signs of increased intracranial pressure without mass or hydrocephalus. A spinal tap was performed, and 25cc of cerebrospinal fluid (CSF) were removed. This provided immediate relief of her visual symptoms and reduced the intensity of her headaches. Her low-back pain, diagnosed as facet syndrome, resolved with a course of spinal manipulation.

Discussion

IIH is also known as primary pseudotumor cerebri syndrome.(1) This disorder frequently presents in young, obese females with symptoms of headache, nausea and vomiting. Ophthalmologic signs are frequent and include papilledema, transient loss of acuity (30 percent experience permanent loss), impaired visual fields, photopsias (flashes), diplopia and a painful eye. Other symptoms of IIH may include pulsatile tinnitus and shoulder or arm pain. Palsies may be seen involving cranial nerves VI, VII and VIII.(2) The worldwide epidemic of obesity is certain to increase the prevalence of this disorder.

The underlying etiopathology of IIH remains controversial. Increased intracranial pressure arises from the decreased CSF resorption that normally occurs in the venous sinus. Increased intracranial dural venous sinus pressure, associated with increased intracranial pressure, also appears to be associated with transverse venous sinus stenosis. Such a mechanism has been postulated as the cause of IIH, or pseudotumor syndrome, regardless of specific etiology.(3)

Dural transverse venous sinus stenosis produces a clinical picture consistent with IIH, but this finding has been controversial, as it was inconsistently detected by routine neuroimaging techniques, including catheter venography and time-of-flight (TOF) MR venography, because of degradation by flow-related artifacts. With the introduction of a newer MR venography technique in 2001, a diagnosis of transverse venous stenosis became possible with high sensitivity and specificity.(4)

However, the question of cause and effect remains today, as consensus is lacking; does the venostenosis cause the increased intracranial hypertension, or does the intracranial hypertension cause the stenosis, or are both variables involved? If the dominant transverse sinus or both transverse sinuses are stenotic, increased intracranial hypertension will occur. Stenosis in the transverse sinus is characterized by two mechanisms: intrinsic narrowing, which may arise from abnormal arachnoid granulations or extrinsic narrowing from intracranial pressure increase causing reversible collapse of the sinus, triggering venous hypertension and reducing CSF absorption.(5) Both mechanisms may result in transverse sinus and superior sagittal sinus hypertension.

MRI of the brain with and without contrast displays signs of increased intracranial pressure in the orbital contents and brain structures. The optic nerve sheaths are frequently tortuous, and there may be flattening of the normally spherical posterior globe, arising in response to papilledema. Notably, no signs of hydrocephalus, meningeal or parenchymal disease are present. There is compression of the ventricles, and a partial empty sella turcica results from increased intracranial hypertension with CSF intrusion deforming the pituitary gland.(6) The CSF analysis is normal, but opening pressures are elevated. The CSF drainage often leads to remission of symptoms in IIH.

Additionally, dural sinus thrombosis (DST) needs to be considered in the differential diagnosis, as it mimics IIH, and if DST is suspected, MR with time of flight (TOF) venogram (MRV) should be obtained to exclude this disorder. In addition to DST, there are a range of differential diagnoses, including endocrinopathies and medications that are associated with IIH.(7) The differential diagnosis of IIH is further challenged as IIH and chronic migraine headache share common clinical manifestations. IIH without papilledema is seen in 14 percent of chronic migraine headache patients.(8)

Imaging Findings

FIGURE 1. MRI Axial FLAIR: There is bilateral narrowing of the frontal horn of the lateral ventricle (long white arrows). The third ventricle is also slitlike (short white arrows).

FIGURE 2. MRI Axial T-2: The scleras are bilaterally flattened posteriorly (short black arrow) with bilateral tortuosity of the optic nerve (long black arrow) and a sella turcica occupied by high signal intensity CSF (long white arrow).

FIGURE 3. MRI Sagittal T-1: The pituitary gland is concavely deformed within the base of the sella turcica, creating a partial empty sella sign (arrows).

Endnotes

1) Friedman DI, Liu GT, Digre KB: Revised diagnostic criteria for the pseudotumor cerebri syndrome in adults and children. Neurology 2013; 81:1-7.

2) Andrews LE, Liu GT, Ko MW. Idiopathic intracranial hypertension and obesity. Neurology 1996; 46: 198–202.

3) Karahalios DG, Rekate HL, Khayata MH, Apostolides PJ. Elevated intracranial venous pressure as a universal mechanism in pseudotumor cerebri of varying etiologies. Horm Res Paediatr. 2014;81(4):217-25.

4) Farb RI, McGregor C, Kim JK, Laliberte M, Derbyshire JA, Willinsky RA, Cooper PW, Westman DG, Cheung G, Schwartz ML, Stainsby JA, Wright GA. Intracranial arteriovenous malformations: real-time auto-triggered elliptic centric-ordered 3D gadolinium-enhanced MR angiography—initial assessment. Radiology.2001 Jul;220(1):244-51.

5) Rohr A, Dörner L, Stingele R, Buhl R, Alfke K, Jansen O. Reversibility of venous sinus obstruction in idiopathic intracranial hypertension. AJNR Am J Neuroradiol. 2007 Apr;28(4):656-9.

6) Ranganathan S, Lee SH, Checkver A, Sklar E, Lam BL, Danton GH, Alperin N. Magnetic resonance imaging finding of empty sella in obesity related idiopathic intracranial hypertension is associated with enlarged sella turcica. Neuroradiology. 2013 Aug;55(8):955-61.

7) Zada G, Tirosh A, Kaiser UB, Laws ER, Woodmansee WW. Cushing’s disease and idiopathic intracranial hypertension: case report and review of underlying pathophysiological mechanisms. J Clin Endocrinol Metab. 2010 Nov;95(11):4850-4.

8) De Simone R, Ranieri A. The role of intracranial hypertension in the chronification of migraine. Neurol Sci. 2015 May;36 Suppl.

Case study provided by Norman Kettner, DC, DACBR, FICC, Chair, Dept. of Radiology, Logan University.

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