Managing Oculomotor Nerve Palsy
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美国医学会眼科杂志中文版980311 Managing Oculomotor Nerve Palsy
The Management of neurologically isolated, nontraumatic oculomotor nerve palsy is a challenge in the wise deployment of expensive and potentially harmful diagnostic tools.
Most cases are caused by ischemia of the nerve and do not require any diagnostic tests. Others are caused by inflammatory or neoplastic meningitis that can be diagnosed with a combination of magnetic resonance imaging and lumbar puncture. But some patients harbor a cerebral aneurysm that could kill them within days and for which timely treatment is curative. In the past, the diagnosis of aneurysm has depended entirely on catheter cerebral angiography, a test that maims or kills in about 1% to 2% of cases, and perhaps more among the elderly and those with ample arteriosclerotic risk factors.
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A recent alternative is magnetic resonance angiography (MRA), a variant of magnetic resonance imaging that highlights blood vessels. Entirely free of complications, it detects more than 95% of cerebral aneurysms that will bleed. But this high sensitivity to aneurysms is possible only with skilled manipulation and review of data gathered with state-of-the-art software. Experience with MRA in aneurysm detection is still limited, and 95% is not 100%! Most experts are not prepared to trust MRA when aneurysm is the prime suspect and the risk of catheter angiography is acceptably low.
, 百拇医药
So how does one decide which patients with isolated oculomotor nerve palsy should undergo catheter angiography, which ones get MRA, and which ones need no brain imaging?
The answer depends on how likely is the diagnosis of ischemia and how unlikely is the diagnosis of aneurysm. Age is not a particularly helpful determinant, in that aneurysms are rare only before age 15 years and after age 75 years. Severe headache is thought to be classic for aneurysm, but it is nearly as common in ischemic palsies. Worsening of the palsy over more than a few days has been invoked as distinctive for compressive lesions, but more than 50% of ischemic palsies do not reach peak severity for 10 days after onset. Arteriosclerotic risk factors (diabetes mellitus, hypertension, heavy smoking, or family history of arteriosclerosis) are a hallmark of ischemic palsies, but are also known to predispose to weakening of the aneurysmal wall, expansion, and rupture.
, http://www.100md.com
That leaves 1 transcendent differentiating feature-the size and reactivity of the pupil. Compressive lesions preferentially damage the rim of the nerve, where the pupillary fibers travel, while ischemic palsies affect the core. Indeed, aneurysms impair the pupillary sphincter in 96% of cases, and among the 4% of cases where the pupil has been spared, the ocular ductions are only partially reduced.
So should every patient with a “pupil-involving” oculomotor nerve palsy undergo catheter angiography? The problem is that pupil involvement has been reported in up to 32% of ischemic oculomotor nerve palsies. Given that ischemic palsies outnumber compressive palsies by at least 9:1, using pupil involvement as a guide would subject a large number of patients to a dangerous procedure.
, 百拇医药
The article by Dr Jacobson in this issue provides valuable input to this management dilemma. In a rigorously designed prospective study, he found that 10 (38%) of 26 patients with ischemic oculomotor nerve palsy associated with diabetes mellitus had pathologic anisocoria, but that only 2 patients had anisocoria greater than 2.0 mm, and it was never greater than 2.5 mm. Previous reports had suggested that anisocoria in these cases is usually minimal, but data were retrospective and haphazard. Although Dr Jacobson's cohort was small, his observations are reliable. Because ischemic oculomotor nerve palsies unassociated with diabetes have a clinical course similar to that of patients with diabetes, we can presume that all patients who have oculomotor nerve palsies with anisocoria of greater than 2.0 mm are outliers for the diagnosis of ischemia. Until MRA is fully validated, subjecting these patients to the hazards of catheter angiography is justified.
投稿截止日期98年10月1日, http://www.100md.com
单位：
关键词：
美国医学会眼科杂志中文版980311 Managing Oculomotor Nerve Palsy
The Management of neurologically isolated, nontraumatic oculomotor nerve palsy is a challenge in the wise deployment of expensive and potentially harmful diagnostic tools.
Most cases are caused by ischemia of the nerve and do not require any diagnostic tests. Others are caused by inflammatory or neoplastic meningitis that can be diagnosed with a combination of magnetic resonance imaging and lumbar puncture. But some patients harbor a cerebral aneurysm that could kill them within days and for which timely treatment is curative. In the past, the diagnosis of aneurysm has depended entirely on catheter cerebral angiography, a test that maims or kills in about 1% to 2% of cases, and perhaps more among the elderly and those with ample arteriosclerotic risk factors.
, http://www.100md.com
A recent alternative is magnetic resonance angiography (MRA), a variant of magnetic resonance imaging that highlights blood vessels. Entirely free of complications, it detects more than 95% of cerebral aneurysms that will bleed. But this high sensitivity to aneurysms is possible only with skilled manipulation and review of data gathered with state-of-the-art software. Experience with MRA in aneurysm detection is still limited, and 95% is not 100%! Most experts are not prepared to trust MRA when aneurysm is the prime suspect and the risk of catheter angiography is acceptably low.
, 百拇医药
So how does one decide which patients with isolated oculomotor nerve palsy should undergo catheter angiography, which ones get MRA, and which ones need no brain imaging?
The answer depends on how likely is the diagnosis of ischemia and how unlikely is the diagnosis of aneurysm. Age is not a particularly helpful determinant, in that aneurysms are rare only before age 15 years and after age 75 years. Severe headache is thought to be classic for aneurysm, but it is nearly as common in ischemic palsies. Worsening of the palsy over more than a few days has been invoked as distinctive for compressive lesions, but more than 50% of ischemic palsies do not reach peak severity for 10 days after onset. Arteriosclerotic risk factors (diabetes mellitus, hypertension, heavy smoking, or family history of arteriosclerosis) are a hallmark of ischemic palsies, but are also known to predispose to weakening of the aneurysmal wall, expansion, and rupture.
, http://www.100md.com
That leaves 1 transcendent differentiating feature-the size and reactivity of the pupil. Compressive lesions preferentially damage the rim of the nerve, where the pupillary fibers travel, while ischemic palsies affect the core. Indeed, aneurysms impair the pupillary sphincter in 96% of cases, and among the 4% of cases where the pupil has been spared, the ocular ductions are only partially reduced.
So should every patient with a “pupil-involving” oculomotor nerve palsy undergo catheter angiography? The problem is that pupil involvement has been reported in up to 32% of ischemic oculomotor nerve palsies. Given that ischemic palsies outnumber compressive palsies by at least 9:1, using pupil involvement as a guide would subject a large number of patients to a dangerous procedure.
, 百拇医药
The article by Dr Jacobson in this issue provides valuable input to this management dilemma. In a rigorously designed prospective study, he found that 10 (38%) of 26 patients with ischemic oculomotor nerve palsy associated with diabetes mellitus had pathologic anisocoria, but that only 2 patients had anisocoria greater than 2.0 mm, and it was never greater than 2.5 mm. Previous reports had suggested that anisocoria in these cases is usually minimal, but data were retrospective and haphazard. Although Dr Jacobson's cohort was small, his observations are reliable. Because ischemic oculomotor nerve palsies unassociated with diabetes have a clinical course similar to that of patients with diabetes, we can presume that all patients who have oculomotor nerve palsies with anisocoria of greater than 2.0 mm are outliers for the diagnosis of ischemia. Until MRA is fully validated, subjecting these patients to the hazards of catheter angiography is justified.
投稿截止日期98年10月1日, http://www.100md.com