Positron Emission Tomography

Ophthalmology Volume 119, Number 7, July 2012 Positron Emission Tomography Dear Editor: We report the correlation of the neuro-ophthalmological findings with a 18F-fluorodeoxyglucose positron emission tomography-computed tomography study (18F-FDG-PET/ CT) in a pediatric patient affected by a pure right homonymous hemianopia manifested after minor head injury and no evidence of any lesions at other neuroimage studies, visual evoked potentials (VEPs), and digital electroencephalogram. The patient was a 14-year-old boy, right-handed, and nearsighted since the age of 10 years. The history is negative for smoking, alcohol, substance abuse, psychiatric illness, previous major traumas, and neurological disease with exception of occasional episodes of headache during the last 2 years. In January 2009 the patient underwent a traumatic event in frontal region (uncontrolled ascent during a volleyball game). The only symptom was a right lateral hemianopia, progressively stabilizing and reaching its definitive status within 2 hours, confirmed by manual and computerized visual field examinations. Brain computed tomography (CT) scan without contrast enhancement highlighted a cystic hypodense mass between the lateral ventricles. Orbital CT scan without contrast enhancement was negative for alterations of bulbar and retrobulbar spaces. Brain magnetic resonance imaging (MRI) showed the persistence of the septum pellucidum, cavum vergae, and velum interpositum. Optica nerves and tracts appeared to be unimpaired. The patient started corticosteroid treatment (prednisone 5 mg/day) and vitamin supplements (thiamine 250 mg, pyridoxine 250 mg, cyanocobalamin 500 ␮g/day), which was withdrawn after a week due to lack of apparent benefit. During the following weeks, the boy presented transient alterations of symptoms: a complete visual loss episode, tunnel vision, and a temporary remission of the visual defect for a few minutes. Moreover, infrared oculography highlighted saccadic movements inconsistent with the condition of hemianopia. Due to these inconsistencies, the suspicion of nonorganic (psychogenic) visual loss arose and the patient was referred for a neuropsychiatric evaluation. This resulted in a diagnosis of somatization disturbance in a borderline personality with a high evolutive risk. As a consequence, he attended regular psychotherapeutical sessions, without improvement of visual symptoms. In February 2009, VEPs with pattern reversal resulted to be normal. In September 2009, he underwent a further MRI examination including functional, tractography, and spectroscopy studies with no positive findings. Manual and computerized visual field examinations repeated in October confirmed the diagnosis of right homonymous hemianopia. The patient was referred to our PET Center in November 2009 and underwent a 3D 18F-FDG-PET/CT study on a Discovery ST-E scanner (General Electric Medical Systems, Milwaukee, MI). Statistical parametric mapping analysis showed areas of hypometabolism on the left primary visual cortex, left associative visual cortex, left parahippocampal gyrus, and thalamus (Fig 1, available at http:// aaojournal.org).1 The 18F-FDG-PET/CT study demonstrated hypometabolic areas, congruent with the symptomatology according 1496 to the visual defect. Altered occipital metabolism could be a consequence of a conversion disorder. Werring et al2 in a functional magnetic resonance imaging (fMRI) study showed an abnormal cerebral response to simple visual stimulation in 5 patients with unexplained visual loss and discrepancy between subjective (acuity and fields) and objective evidence of visual loss (normal findings at VEPs and papillary light responses). The authors explain their findings as the evidence of more complex visual processing strategies in patients with psychogenic visual loss, involving inhibitory modulation of primary visual areas. Our patient presented as well with a discrepancy between subjective and objective evidence of visual loss but the fMRI demonstrated negative findings. Furthermore all 5 patients, presented by Werring2 fulfilled the DSM-IV criteria (American Psychiatric Association, 1994) for conversion disorder, whereas our patient did not. For these reasons the fascinating hypothesis of psychogenic visual loss has been excluded. Transient homonymous hemianopia has usually reported as one of the possibilities manifestation of the aura phase of migraine.3 The patient’s remote history showed that the headache was bilateral and causing symmetric pain, so is not consistent with migraine.4 Furthermore, the boy didn’t experience any of these episodes during the day of PET exam. In the absence of any demonstrable structural lesion we concluded that the hemianopia in our patient is secondary to subtle posttraumatic occipital dysfunction. According to our analysis, the PET/CT seems to be superior to CT and MRI in the evaluation of unexplained visual loss in this patient. Our results are in keeping with those of Itoh et al,5 who demonstrated that, using [18F]-2-fluorodeoxyglucose, PET appeared to be more sensitive in detecting lesions responsible for cortical hemianopia than CT and MRI. In our case, PET/CT had a predominant role in the diagnostic work-up and we believe led to the correct diagnosis. Currently, the patient returned to play volleyball, has a good functioning at school and has solved the hemianopic dyslexia by using cardboard masks of different sizes. ANGELINA CISTARO, MD Turin, Italy NATALE QUARTUCCIO, MD Messina, Italy SARA VESCO, MD Turin, Italy MARCO PAGANI, PHD Rome, Italy PIERCARLO FANIA, MD LUCIANO DONATI, MD Turin, Italy FLAVIO M. NOBILI, MD Genoa, Italy Letters to the Editor SERGIO DUCA, MD GIOVANNA CARRARA, MD MARIA C. VALENTINI, MD Turin, Italy References 1. Signorini M, Paulesu E, Friston K, et al. Rapid assessment of regional cerebral metabolic abnormalities in single subjects with quantitative and nonquantitative [18 F] FDG PET: a clinical validation of statistical parametric mapping. Neuroimage 1999;9:63– 80. 2. Werring DJ, Weston L, Bullmore ET et al. Functional magnetic resonance imaging of the cerebral response to visual stimulation in medically unexplained visual loss. Psycholol Med 2004;34:583–9. 3. Goodwin D. Transient complete homonymous hemianopia associated with migraine. Optometry 2011;82:298 –305. 4. Headache Classification Committee of the International Headache Society. Classification and diagnostic criteria for headache disorders, cranial neuralgias and facial pain. Cephalalgia 1988;8(Suppl 7):1–96. 5. Itoh M, Kiyosawa M, Yamaguchi K et al. Positron tomography for ophthalmology. Jpn J Ophthalmol 1987;31:114 –23. Choroidal Thickness After Scleral Buckling Dear Editor: Scleral buckling surgery is a well-established procedure for the treatment of rhegmatogenous retinal detachment. A study with laser Doppler flowmetry reported reduction of choroidal blood flow in the foveal region,1 the physiological state of which might be negatively affected. The choroidal thickness at the foveal region (ChTF) would be related with a change in choroidal circulation at the fovea.2 In the present study, we evaluated the ChTF change after scleral buckling surgery and evaluated the physiological change of the choroid at the foveal region. We prospectively examined 11 Japanese patients, including 10 males and 1 female, aged 16 –72 years (mean, 58.5 years) who underwent surgery for unilateral rhegmatogenous retinal detachment. The patients with retinal detachment having macular involvement were excluded because retinal detachment might interfere with clear images of the choroid in enhanced depth imaging optical coherence tomography (EDI-OCT) imaging. Moreover, patients with glaucoma, uveitis, macular degeneration, retinal vascular disorders, other ocular disorders, or a history of ophthalmic surgery were excluded. All surgeries were performed with local anesthesia. Retinal breaks were identified in all patients and were treated with transscleral cryotherapy. A 7-mm silicon tire (no. 276; Mira, Waltham, MA) or 5-mm silicon sponge (no. 506; Mira) was used without an encircling band. The extent of scleral buckling was 360 degree for 1 eye, 240 degree for 1 eye, 150 degree for 3 eyes, and 90 degree for 6 eyes. Subretinal fluid was drained externally in 8 eyes. No vortex veins were damaged and no rectus muscles were removed. Each retina was reattached completely after 1 operation without complications. The ChTF was measured with EDI-OCT imaging3 (3-D OCT 2000; Topcon Corp, Tokyo, Japan). Each OCT image consisted of 1024 A-scans corresponding to 6 mm of the retina, and EDI-OCT images were obtained by averaging 50 B-scan images. The ChTF was measured in both eyes of all patients before surgery and 1, 2, and 4 weeks after surgery. All studies were performed according to the tenets of the Declaration of Helsinki and were approved by the institutional review board of Tokyo Medical University. The data were analyzed with a paired t-test and repeated-measures analysis of variance, and P⬍0.05 were considered significant. The ChTF (mean [SD]) in treated eyes was 270 (58) ␮m, 296 (61) ␮m, 279 (69) ␮m, and 267 (64) ␮m at before surgery, and 1, 2, and 4 weeks after surgery, respectively. The ChTF was significantly thicker 1 week after scleral buckling than before scleral buckling (P ⫽ 0.0008). The ChTF gradually decreased 2 and 4 weeks after surgery and returned to preoperative thickness 4 weeks after surgery. The ChTF was significantly lower 4 weeks after scleral buckling than 1 week after surgery (P ⫽ 0.006). The ChTF (mean [SD]) in fellow eyes was 282 (65) ␮m, 280 (68) ␮m, 281 (72) ␮m, and 276 (71) ␮m at before surgery, and 1, 2, and 4 weeks after surgery, respectively. In fellow eyes, no significant difference was observed between before and after scleral buckling surgery. No significant differences in ChTF were observed between treated eyes and fellow eyes before scleral buckling (P ⫽ 0.46). In the present study, we evaluated changes in the ChTF after scleral buckling surgery. The ChTF increased temporarily after scleral buckling surgery and returned to preoperative thickness 4 weeks after surgery. Despite the absence of macular involvement or clinically identifiable complications, the physiological state of the choroid at the foveal region might have been altered. The first mechanism for increasing the ChTF would possibly be increased choroidal blood flow resistance by mechanical compression from the scleral buckling.1,4 Congestion of choroidal blood flow by elevated choroidal blood pressure might induce a foveal thickness change. Inflammation and transient reduction of intraocular pressure during surgery would additionally contribute to the ChTF increase. Further studies are required to confirm the significance of this change in the clinical course and visual performance after scleral buckling surgery. MASAHIRO MIURA, MD, PHD GO ARIMOTO, MD RINTARO TSUKAHARA, MD REI NEMOTO, MD TAKUYA IWASAKI, MD Ami, Japan Tokyo, Japan HIROSHI GOTO, MD Tokyo, Japan References 1. Sugawara R, Nagaoka T, Kitaya N, et al. Choroidal blood flow in the foveal region in eyes with rhegmatogenous retinal detachment and scleral buckling procedures. Br J Ophthalmol 2006;90:1363– 4. 2. Nickla DL, Wallman J. The multifunctional choroid. Prog Retin Eye Res 2010;29:144 – 68. 1497 Ophthalmology Volume 119, Number 7, July 2012 Figure 1. Statistical parametric mapping analysis showed areas of hypometabolism on the left primary visual cortex, left associative visual cortex, left parahippocampal gyrus, and thalamus. 1497.e1