the epileptics probably represented a postictal effect. Of the six epileptics who had a second EEG at least two weeks after the initial tracing, four had resolution of the delta focus; none had focal CT abnormalities. One of the two patients with persistent delta activity had a CT scan that showed a focal abnormality. Masdeu et al6 reported a 20% inci¬ dence of normal CT scans in cases of acute ischemie strokes and in our study the CT scan failed to demon¬ strate a focal abnormality in six of 32 patients (19%) with acute ischemie infarctions. Thus, the EEG revealed dysfunction not yet detectable mor¬ phologically. This study emphasizes the impor¬ tance of continuous focal delta activi¬ ty and its frequent association with a gross structural lesion, while demon¬ strating the complementary nature of the CT scan and the EEG in diagno¬ sis. References 1. Joynt RJ, Cape CA, Knott JR: Significance of focal delta activity in adult electroencephalogram. Arch Neurol 1965;12:631-638. 2. Weisberg LA, Nice C, Katz M: Seizure disorders and correlation with specific EEG patterns, in Cerebral Computed Tomography. Philadelphia, WB Saunders Co, 1978, pp 291-292. 3. Yang PJ, Berger PE, Cohen ME, et al: Computerized tomography and childhood seizure disorders. Neurology 1979;29:1084-1088. 4. Bogdanoff BM, Stafford CR, Green L, et al: Computerized transaxial tomography in the evaluation of patients with focal epilepsy. Neurology 1975;25:1013-1017. 5. Scollo-Lavizzari G, Eichhorn K, Wuthrich R: Computerized transverse axial tomography (CTAT) in the diagnosis of epilepsy. Eur Neurol 1977;15:5-8. 6. Masdeu JC, Azar-Kia B, Rubino F: Evaluation of recent cerebral infarction by computerized tomography. Arch Neurol 1977;34:417-421. Central Dazzle A Thalamic Syndrome? Jeffrey L. Cummings, MD, John W. Gittinger, Jr, MD \s=b\ A patient who experienced painless intolerance to light (dazzle) three months after a right posterior cerebral artery occlusion was shown by computerized tomography to have right occipital and right thalamic infarctions. His symptoms improved with amitriptyline hydrochloride and perphenazine therapy. The sensitivity to light, delayed onset, response to therapy, and presence of a thalamic lesion are analogous to the thalamic pain syndrome and suggest that central dazzle is a variant of the thalamic syndrome. (Arch Neurol 1981;38:372-374) xcessive sensitivity to light may T^i -Li be secondary to true photophobia or to photophobia due to dazzle.1 True photophobia is pain on exposure to light typically associated with inflam¬ matory conditions of the anterior seg¬ ment of the eye. Dazzle is the painless Accepted for publication July 29, 1980. From the Department of Neurology, Boston University School of Medicine (Dr Cummings), the Departments of Ophthalmology and Neurology, Tufts University School of Medicine, Boston (Dr Gittinger), and the Boston Veterans Administration Medical Center (Drs Cummings and Gittinger). Dr Cummings is currently with the Neurobehavior Unit, Brentwood Veterans Administration Medical Center and with the Department of Neurology, UCLA, Los Angeles. Reprint requests to Neurobehavior Unit, Brentwood Veterans Administration Medical Center, Ward 208C, 11301 Wilshire Blvd, Los Angeles, CA 90073 (Dr Cummings). exaggeration of brightness as de¬ scribed by persons with toxic amblyopia, albinism, rod monochromatism, and corneal, lenticular, and vitreous opacities that disperse light. Sensitivi¬ ty to light is unusual as a consequence of CNS disease. Walsh and Hoyt2 mention its occurrence in trigeminal neuralgia, migraine, meningitis, subarachnoid hemorrhage, sellar and su¬ prasellar tumors, during and after retrobulbar neuritis, and following head trauma. We describe a patient who experienced dazzle after an infarction in the territory of the right posterior cerebral artery (PCA). Clini¬ cal, radiologie, and therapeutic evi¬ dence suggests that a thalamic lesion accounts for the light intolerance. REPORT OF A CASE A 62-year-old right-handed man was well until November 1977, when without warn¬ ing a "herringbone" or "tire tread" pattern appeared in the left lower portion of his vision and lasted for several seconds. There were no other associated symptoms. The pattern transiently recurred later that evening. The following day his vision seemed "blurry" or "fuzzy," and two days later he got lost on his way to work. He was seen by a neurologist and an ophthalmolog¬ ist, who found a dense congruous left superior quadrantanopsia. No other cranial nerve, motor, sensory, or reflex abnormali¬ ties were noted. His mental status was unremarkable, except for a tendency to get lost in a hospital well known to him. A computerized tomographic (CT) scan of the head revealed an area of diminished densi- Downloaded From: http://archneur.jamanetwork.com/ by a New York University User on 06/13/2015 ty in the territory of the right posterior cerebral artery. In January 1978, three months after the initial event, the patient first noted an unusual sensitivity to bright lights. This condition progressed rapidly and became severe during the course of one week. The sensitivity was continuous, involved all the remaining visual field, and was uniform throughout. He described the light intoler¬ ance as disagreeable rather than truly painful and "like going into the sunshine from a dark room." He acquired five pairs of glasses of varying tints and wore a sun visor. He kept his shades drawn in the house and closed his eyes while outside in the daylight. Coincident with the develop¬ ment of the light sensitivity he also noted a "milky haze" that partially obscured his vision. He had difficulty adjusting to changes in illumination, and light contrasts increased so that shadows seemed darker and lighted areas lighter. Colors appeared less distinct. A former amateur oil painter, he could no longer mix and match paints correctly. He continued to have mild difficulty finding his way in familiar areas, and he occasionally had trouble recognizing familiar people. On one occasion he "saw" his wife's arm in his blind field. No other hallucinations and no metamorphopsias were reported. Prior to his illness the patient had been employed for many years as an inventory controller for a large company. He described himself as a perfectionist, but there was no evi¬ dence of a premorbid psychiatric disor¬ der. The patient was referred for further evaluation of his visual disturbance. Men¬ tal status, motor, somatic sensory, and reflex examinations were normal. Color naming was intact. When tested under were 120 240 105 90 75 60 120 105 255 270 285 300 240 255 75_60 270 25 30 Fig 1.—Visual fields showing congruent left superior homonymous quadrantanopsia. Fig 2.—Computerized tomograms showing infarction in distribution of right posterior cerebral artery. Central image demonstrates loss of substance in upper brainstem on right, producing concave indentation laterally at level of mesodiencephalic junction. optimal conditions he had no difficulty matching faces with similar expressions or recognizing pictures of famous people or the faces of ward personnel. His perform¬ ance on a battery of neuropsychological tests was average or above (verbal IQ, 130; performance IQ, 110; full-scale IQ, 123) except for a substantial impairment on the visual memory portions of the Wechsler Memory Scale. Fundi, extraocular movements, optokinetic nystagmus, pupillary responses, and slitlamp examination results were normal. Visual acuity was 20/20 in each eye. Perimetry revealed a congruous left homony¬ mous quadrantanopsia (Fig 1). Stereoscop¬ ic vision was impaired (he failed to detect arcs of less than 100 s on the Titmus stereo tests). Color vision as tested with Ishihara's pseudoisochromatic plates was normal, but he scored in the impaired range on the Farnsworth-Munsell 100 Hue Test of color hue discrimination (score, 132; normal, 20 to 100). Dark adaptation was normal in both eyes. An EEG revealed asymmetric 9-Hz alpha activity of lower voltage on the right and an asymmetric response to photic stimula¬ tion with a smaller response amplitude on the right. An electroretinogram was normal. Pattern-reversal visual evoked potentials were unrecordable for 12-minute checks (stimulus squares subtending 12 minutes of visual angle) and normal for 48-minute checks. A CT scan (Fig 2) showed an area of diminished density in the occipital and posterior inferior medial temporal regions of the right hemisphere. There was also loss of substance in the right upper brainstem laterally at the level of the mesodiencephalic junction, with widening of the quadrigeminal cistern. Downloaded From: http://archneur.jamanetwork.com/ by a New York University User on 06/13/2015 A variety of medications were pre¬ scribed in an attempt to modify the light intolerance. Therapeutic levels of pheny¬ toin sodium and diethylcarbamazepine citrate had no effect. Ethosuximide pro¬ duced a minimal ameliorating response. Partial relief was obtained with a combina¬ tion of amitriptyline hydrochloride (150 mg/day) and perphenazine (6 mg/day). On this regimen, however, acute urinary retention developed. When the medications were stopped, the light sensitivity prompt¬ ly returned. The patient then underwent a transurethral prostatectomy for benign prostatic hypertrophy. Following surgery, the combination of amitriptyline and per¬ phenazine was reinstituted and the exces¬ sive sensitivity to brightness again dimin¬ ished. There was no change in the milky haze of his vision or in the difficulty adjusting to light contrasts. COMMENT This patient presented a variety of disorders of higher visual function, including visual hallucinations, topo¬ graphical disorientation, a history suggestive of prosopagnosia, and im¬ paired color perception. His most dis¬ abling problems were marked light intolerance, the appearance of a milky obscuring his vision, and the exaggeration of light and dark con¬ haze trasts. The latter abnormalities devel¬ oped three months after an infarction in the distribution of the right PCA. Evaluation revealed a failure to elicit visual evoked potentials with small stimulus squares, impaired perform¬ ance on the Farnsworth-Munsell color hue discrimination test, altered depth perception, and disturbed visual mem¬ ory. The discomfort produced by light was partially ameliorated by treat¬ ment with a combination of amitrip¬ tyline and perphenazine. A CT scan demonstrated an occipital infarction and a lesion at the mesodiencephalic junction. Several of the patient's deficits can be explained by the infarction in the distribution of the right PCA, where¬ as others suggest bilateral ischemie injury. Impaired visual memory,3 de¬ fective depth perception/ visual hallu¬ cinations,5 and failure on the Farn¬ sworth-Munsell hue discrimination test" have been reported with unilat¬ eral right posterior lesions. Topo¬ graphic disorientation, a common ac¬ companiment of central achromatop¬ sia7 and of prosopagnosia,8 occurs in patients with bilateral posterior cere¬ bral damage. The milky haze and con¬ trast alterations complained of by the patient have also been described in patients with bilateral occipital in¬ farctions. Critchley" noted that some patients with visual agnosia-like syn¬ dromes saw things as "darker, small¬ er, and misty" or "as though there was a thin layer over it all." Similarly, the artist with visual agnosia described by Wapner et al1" complained that "ev¬ erything seemed dim, as if it were twilight." The lesions producing visual agnosia involve the region of the inferior longitudinal fasciculus bilat¬ erally." The unusual light sensitivity expe¬ rienced by this patient beginning sev¬ eral months after the PCA occlusion resembles closely the delayed onset of dysesthesia and hyperpathia follow¬ ing thalamic infarction and suggests that the observed mesodiencephalic lesion was responsible for the dazzle. The syndrome of thalamic infarction'-' is characterized by an acute transient hemiparesis, disturbed sensation, and mild hemiataxia of the weak limbs followed several months later by severe persistent pains involving the previously paretic side. Sensory stim¬ ulation increases the pain (hyperpathia). Pathological study revealed in¬ farction in the posterior and lateral nuclei of the thalamus in the distribu¬ tion of the thalamogeniculate and thalamoperforate branches of the PCA.11 In most cases of the thalamic syndrome, somatic sensation alone is involved. Occasionally, however, other sensory modalities are implicated. Riddoch14 noted that a sudden bright light, a loud or unexpected noise, and less often intense smell or strong taste caused intense discomfort, and Head" described a patient who could no long¬ er go to worship because he "could not stand the hymns on his affected side." Treatment of the pain in the thalamic syndrome is difficult, but recently some success has been achieved with the combination of a tricyclic antidepressant and a phenothiazine1" used in this patient. The contribution of the cortical damage to the light sensitivity cannot be determined with certainty. "Pseudothalamic" central pain after cortical injury has been described171" but is infrequent, while dysesthesia and hyperpathia following thalamic lesions are common. Furthermore, patients with occipital infarctions have been extensively studied, and central dazzle rarely has been noted. The phenome¬ non was not mentioned in patients with cortical lesions producing agno¬ sia, central achromatopsia, visual hal¬ lucinations, topographical disorienta¬ tion, or in large series of patients with hemianopsias.1'"'8"11192" In a report by Meadows,7 one patient with prosopag¬ nosia complained that colors were excessively bright on sunny days, but the subcortical extent of the patient's lesion was unknown. Huber-' de¬ scribed a patient with excessive light sensitivity who "would cover his eyes with a dark cloth, even indoors." The patient had a midbrain tumor, and Huber proposed a regulatory role for mesencephalic and thalamic struc¬ tures with light intolerance resulting from disrupted regulation. In summary, this patient had no ocular disease and no other distur¬ bance known to cause photophobia or dazzle. The infarction in the cortical territory of the right PCA contributed to the complex visual syndrome, but by itself was an unlikely cause of the light intolerance. The sustained sensi¬ tivity to sensory stimulation, delayed onset, response to therapy, and près- Downloaded From: http://archneur.jamanetwork.com/ by a New York University User on 06/13/2015 enee of a diencephalic lesion are analo¬ gous to the thalamic pain syndrome and suggest that central dazzle is a consequence of thalamic injury. Paul Vinger, MD, referred the patient; D. Frank Benson, MD, John Carter, MD, and Thedi Landis, MD, aided in the clinical evaluation; Edith Kaplan, PhD, and William Milberg, PhD, performed the neuropsychological assessment; Harvey Levine, MD, interpreted the CT scan; Samuel Sokol, MD, did the visual evoked poten¬ tial studies; Lome Direnfeld, MD, brought Head's cases to our attention; and Gayle Lawrence prepared the manuscript. Nonproprietary Names and Trademarks of Drugs Amitriptyline hydrochloride—Amavil, Amitid, Amitril, Elavil, Endep. Ethosuximide—Zarontin. References 1. Lebensohn JE: The nature of photophobia. Arch Ophthalmol 1934;12:380-390. 2. Walsh FB, Hoyt WF: Clinical Neuro-ophthalmology, ed 3. Baltimore, Williams & Wilkins Co, 1969, vol 1, pp 413-416. 3. Milner B: Visual recognition and recall after right temporal lobe excision in man. Neuropsy- chologia 1968;6:191-209. 4. Carmon A, Becktoldt HP: Dominance of the right cerebral hemisphere for stereopsis. Neuropsychologia 1969;7:29-39. 5. Lessell S: Higher disorders of visual function: Positive phenomena, in Glaser JS, Smith JL (eds): Neuro-ophthalmology. St Louis, CV Mosby Co, 1975, vol 8, pp 27-44. 6. Scotti G, Spinnler H: Colour imperception in unilateral hemisphere-damaged patients. J Neurol Neurosurg Psychiatry 1970;33:22-28. 7. Meadows JC: Disturbed perception of colours associated with localized cerebral lesions. Brain 1974;97:615-632. 8. Benson DF, Segarra J, Albert ML: Visual agnosia-prosopagnosia. Arch Neurol 1974;30:307\x=req-\ 310. 9. Critchley M: The problem of visual agnosia. J Neurol Sci 1964;1:274-290. 10. Wapner W, Judd T, Gardner H: Visual agnosia in an artist. Cortex 1978;14:343-363. 11. Albert ML, Soffer D, Silverberg R, et al: The anatomic basis of visual agnosia. Neurology 1979;29:876-879. 12. Wilkins RH, Brody IA: The thalamic syndrome. Arch Neurol 1969;20:559-562. 13. Langworthy OR, Fox HM: Thalamic syndrome. Arch Intern Med 1937;60:203-224. 14. Riddoch G: The clinical features of central pain. Lancet 1938;1:1093-1098, 1150-1156, 1205\x=req-\ 1209. 15. Head H: Studies in Neurology. London, Hodder and Stoughton, 1920, p 560. 16. Samuels MA: Manual of Neurologic Therapeutics. Boston, Little Brown & Co, 1978, p 198. 17. Critchley M: The Parietal Lobes. London, Edward Arnold, 1953, pp 152-155. 18. Davison C, Schick W: Spontaneous pain and other subjective sensory disturbances. Arch Neurol Psychiatry 1935;34:1204-1237. 19. Trobe JD, Lorber ML, Schlezinger NS: Isolated homonymous hemianopia. Arch Ophthalmol 1973;89:377-381. 20. Smith JL: Homonymous hemianopia. Am J Ophthalmol 1962;54:616-623. 21. Huber A: Eye Symptoms in Brain Tumors. St Louis, CV Mosby Co, 1961, p 29.