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Editor,—The common features associated with cerebral venous thrombosis (CVT) are headache, papilloedema, motor or sensory deficits, seizures, and conscious disturbance.1Ophthalmological manifestations including diplopia, subnormal visual acuity, or visual field defect are primarily the consequence of increased intracranial pressure (IICP).2 Visual disorientation, psychic gaze paralysis, and inferior altitudinal hemianopsia may develop if cerebral infarction is complicated in the parieto-occipital (P-O) region.3 We describe an unusual oriental case of CVT presenting uncommon transient visual loss to stress the diversity of the manifestations of CVT.
A 54 year old woman suffered from sudden onset of severe headache and progressive visual loss in both eyes within 1 day. Her past history was unremarkable but her family history was significant for thrombophilia, pulmonary embolism (her father), and deep vein thrombosis (her son). She had just undergone hormone replacement therapy with oral conjugated oestrogen and medroxyprogesterone for 1 month.
On admission, she was conscious. Blood pressure was 156/84 mm Hg. Physical and neurological examinations were normal. Ophthalmic examinations disclosed corrected visual acuity of 1/60 in the right eye and counting fingers in the left eye. Both eyes exhibited orthophoria with full and free extraocular movement in all directions. The pupils were isocoric, 4 mm in diameter, with sluggish light reflex of both eyes, there being no relative afferent pupillary defect. Slit lamp biomicroscopy, indirect ophthalmoscopy, and fluorescein angiography did not reveal any abnormality. A Goldmann visual field test showed left homonymous hemianopsia. An urgent brain computed tomography (CT) revealed a haematoma in the right P-O region with marked cerebral oedema and a left shifted midline. A brain magnetic resonance image (MRI) indicated hyperintensities on T1 and T2 weighted images in the corresponding area (Fig 1), although the brain MRI was also characterised by a lesion in the left P-O region, which revealed a hypointense signal without contrast enhancement on T1 weighted images (T1WI) and hyperintense signal on T2 weighted images (T2WI), indicating cerebral oedema or infarction (Fig 1). A further brain magnetic resonance venography (MRV) indicated a loss of signal in the posterior half of the superior sagittal sinus and adjacent cortical veins (Fig 2). Other laboratory investigations including blood cell counts, PT, APTT, and immunological profiles all returned normal results.
Warfarin and glycerol were administered. Her headache subsided 4 days later. A follow up brain CT 2 weeks after admission revealed the subsidence of cerebral oedema and a partial resolution of the haematoma. The patient's vision recovered to 6/6 in both eyes 3 weeks subsequently, but the visual field defect persisted. Serial quantitative measurements of anticoagulant factors revealed an inadequate antithrombin III (AT III) level of 57% (normal range 80–120%). Her son and daughter also demonstrated a subnormal AT III level. Now she is doing well with a daily dose of warfarin (5 mg/day).
Acute reversible visual loss in this case was an unusual presentation for CVT. Pathogenetically, CVT may result in visual disturbance through several different mechanisms including long term IICP and complicated venous infarction involving the bilateral visual cortex. The sluggish light reflex with normal disc appearance for this patient may indicate optic nerve dysfunction secondary to acute IICP. Although acute IICP itself may result in transient visual obscuration, severe visual loss only complicates end stage IICP with optic atrophy.2 On the other hand, CVT associated venous infarction involving the bilateral primary visual cortex may lead to cortical blindness; however, for the present case, the rapid recovery of vision and the absence of any low density regions representing cerebral infarction over the left P-O region on the follow up brain CT excluded such a possibility. The possible explanation for the acute, reversible visual loss in this case may be the severe left occipital lobe oedema secondary to venous congestion, concurrent with a haemorrhagic infarction in the right P-O region that resulted in the left hemianopsia. In fact, it has been reported that patients with eclampsia may demonstrate transient blindness due to occipital oedema, which may then resolve within 24 hours after delivery and the application of medication to reduce cerebral oedema.4Further, when relating brain MRI of venous sinus occlusive diseases to the underlying pathophysiology, Yuh et alnoted a rapid resolution of the hyperintense signal on T2WI after restoration of venous drainage, which indicated that the signal change on T2WI represented reversible venous congestion and pressure driven interstitial oedema. Thus, these authors concluded that early intervention might resolve the clinical symptoms and normalise the MR appearance of certain venous sinus occlusive diseases.5Tissue damage for these patients was reported to be predominantly resulted from the haematoma, as was the right P-O haematoma and the persistent left homonymous hemianopsia in this case.5
Of note, a combination of a hereditary AT III deficiency, which is extremely rare in orientals, and hormone replacement therapy may have been the culprits leading to an extensive CVT for this patient.6 In addition, in patients with superior sagittal sinus thrombosis, only one third have a thrombosis involving the posterior third of the sinus, just as in the present case.7 The acute reversible visual loss, a rarely reported presentation of CVT, could be attributed to the coexistence of extensive cerebral oedema and the relatively unusual site of venous thrombosis in the present case.
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