Description and clinical application of the Pulfrich effect.

BACKGROUND: In 1922, German physicist Carl Pulfrich described an illusory binocular perceptual disturbance in which an object moving across an observer's field of vision is perceived as traveling along a curved trajectory. OBJECTIVE: To review the discovery of the Pulfrich effect, and subsequent clinical applications. METHODS: We translated Pulfrich's description and searched for subsequent publications using electronic databases and review of reference lists in identified publications. RESULTS: In 1901, Pulfrich developed an optical device to accurately compare stereoscopic photographs, but brightness difference between plates caused distance misperceptions that interfered with precise measurements. Pulfrich proposed that this Stereo-Effekt resulted from interocular differences in perceptual latency. He induced the effect by placing a smoked glass in front of one eye. The resulting perceptual disparity creates an apparently curved trajectory of an object moving sideways across the field of vision. Pulfrich also recognized that visual pathway disorders can produce a pathologic Stereo-Effekt. In 1925, Grimsdale demonstrated this in a man with unilateral retrobulbar optic neuritis and suggested treatment with a neutral density filter (NDF) over the good eye. Not until the 1970s, however, was the Pulfrich effect evaluated as a diagnostic test for retrobulbar optic neuritis and the therapeutic efficacy of an NDF confirmed. CONCLUSION: Although the clinical importance of the Pulfrich effect was suggested by Pulfrich and quickly confirmed, it took decades before its diagnostic utility and the efficacy of an NDF were assessed. Recognition remains clinically important to minimize safety risks and mislabeling, and because resulting misperceptions can be easily treated.

Stenting and angioplasty for idiopathic intracranial hypertension: a case series with clinical, angiographic, ophthalmological, complication, and pressure reporting.

BACKGROUND: Previous studies have demonstrated that cerebral dural sinus stenosis (DSS) may be a potential patho-physiological cause of idiopathic intracranial hypertension (IIH). Endovascular therapy for DSS is emerging as a potential alternative to treat IIH. Here, we present the results of our case series. METHOD: We prospectively collected angiographic and manometric data on patients that underwent angioplasty/stenting for IIH. All patients had failed maximal medical therapy (MMT) and had confirmed sinus stenosis. Demographic, clinical and radiological presentation, and outcomes were collected retrospectively. RESULTS: A total of 18 patients underwent 25 procedures. Demographics revealed a mean age of 30 (range 15-59), 83% (15/18) were female, 72% (13/18) were white, and mean body mass index of 36 (range 23-59.2). All patients presented with classic IIH. Symptom improvement or resolution was reported in 94% (17/18) of patients. All patients had resolution and/or stabilization/improvement of their papilledema. Headaches related to increased pressure improved in 56% (10/18). Re-stenosis and retreatment occurred in 33% (6/18). No procedural related complications were reported. CONCLUSION: Dural sinus angioplasty and stenting is relatively safe, feasible, and clinically efficacious for patients with symptomatic sinus stenosis who have failed standard therapy. The long-term durability of patency and clinical improvement remains unknown.

Venous sinus pulsatility and the potential role of dural incompetence in idiopathic intracranial hypertension.

BACKGROUND: Idiopathic intracranial hypertension (IIH) remains a poorly understood and therapeutically challenging disease. Enthusiasm has emerged for endovascular therapy with stent reconstruction of dural sinus narrowing; however, a complete understanding of the hydrodynamic dysequilibrium is lacking. OBJECTIVE: To review and characterize catheter manometry findings including pulsatility changes within the venous sinuses in IIH. METHODS: Cases of venous sinus stent implantation for IIH were retrospectively reviewed. RESULTS: Three cases of venous sinus stent implantation for treatment of IIH are reported. All cases demonstrated severe narrowing (>70%) within the transverse sinus and a high pressure gradient across the lesion (>30 mm Hg). Stent implantation resulted in pulsatility attenuation, correction of pressure gradient, and improvement of flow. CONCLUSION: We report the finding of high venous sinus pulsatility attenuation after stent implantation for dural sinus narrowing and propose the hypothesis that this finding is a marker of advanced dural sinus incompetence. This characteristic may be useful in identifying patients who would benefit from endovascular stent remodeling.

Chiari type I malformation: overview of diagnosis and treatment.

Chiari Type I malformation (Chiari I) is a congenital hindbrain anomaly characterized by downward displacement of the cerebellar tonsils through the foramen magnum. This can lead to compression of cerebellar components, the lower brainstem, and the upper cervical spinal cord. In turn, a variety of neurological deficits and permanent nervous system damage may evolve. This review article discusses the etiology, diagnosis, and treatment of patients with Chiari I malformation. Its protean manifestations cause significant overlap with multiple sclerosis, chronic fatigue syndrome, and numerous other conditions. Accordingly, the diagnosis of Chiari I is difficult to establish by clinical evaluation alone. Demonstration of the characteristic hindbrain abnormalities, however, is easily accomplished with magnetic resonance imaging. Neuroimaging should therefore be considered in patients with cerebellar, brainstem, and cervical cord dysfunction. Surgical treatment is indicated in symptomatic patients with radiographic evidence of hindbrain abnormalities. Posterior fossa decompression has also been performed in patients with fibromyalgia and chronic fatigue syndrome based solely on overlapping symptoms with Chiari I. This practice remains controversial. Appraisal of surgical outcome requires postoperative neuroimaging and long-term patient follow-up to assess the permanency of improvement. Preliminary study results of the impact of surgical technique on patient outcome are reported. Ongoing research is devoted to a better understanding of the pathophysiology of Chiari I malformation and the development of more effective medical and surgical treatments.