MRI在上斜肌麻痹中的应用研究

目的 探讨先天性上斜肌麻痹病因的解剖基础,研究上斜肌麻痹患者上斜肌影像学的形态变化。 方法 测量正常人和上斜肌麻痹患者的上斜肌最大横截面积和肌容积,确定正常值。应用表面线圈磁共振(MRI)和计算机图像处理技术及三维物体测量方法,采用SPSS统计分析软件包进行统计学分析。 结果 正常人上斜肌的最大横截面积为(19.78±1.93)mm2,肌容积为(233.23±14.96)mm3。上斜肌麻痹患者上斜肌的最大横截面积为(15.74±6.31)mm2,先天性者(16.91±5.73)mm2,后天性者(14.16±10.40)mm2;肌容积为(188.39±63.65)mm3,先天性者(200.30±60.49)mm3,后天性者(137.81±57.23)mm3,同正常组比较均明显减小(P<0.05),但先天性和后天性上斜肌麻痹患者间无明显差别,且先天性上斜肌麻痹组中上斜肌容积与年龄无相关性。 结论 上斜肌麻痹患者的上斜肌影像形态明显缩小。先天性上斜肌麻痹患者可能存在肌肉、肌腱、直肌滑车多种先天性解剖异常。     

先天性上斜肌麻痹患者双眼视功能情况

目的：探讨先天性上斜肌麻痹患者双眼视功能的存在情况。方法：对176例先天性上斜肌麻痹的患者,进行了回顾性分析。结果：176例患者中87例（49.4%）具有双眼视功能,89例（50.6%）无双眼视功能,168例有代偿头位。结论：先天性上斜肌麻痹患者仅部分有双眼视功能。     

滑车神经麻痹

上斜肌受滑车神经支配,上斜肌麻痹在垂直眼外肌麻痹中比较常见,可分为先天性和后天性二种,前者多见于儿童,且常为部分性,是造成儿童斜颈的原因之一;后者见于各种年龄组,以外伤后多见,是造成垂直性及旋转性复视的主要原因。本文就滑车神经的解剖、滑车神经麻痹的原因、诊断、鉴别诊断和治疗加以综述。     

垂直扫视运动检查在上斜肌麻痹中的应用

目的 建立不同年龄正常人垂直扫视运动峰速的参数;了解该检查的可重复性;研究上斜肌麻痹患者垂直扫视运动的峰速变化特点.方法 采用运动EOG法检查22例正常人（青年组12例和中老年组10例）及18例上斜肌麻痹患者的垂直扫视运动峰速,正常人中10例在1周至1个月内重复本检查.结果 正常人4个方位的平均峰速均较对称,各方位向上与向下运动、左右眼各相对应方向、中老年组与青年组相对应方向、重复性试验者前后两次检查相对应方向平均峰速差异均无统计学意义;上斜肌麻痹眼内下方向下运动平均峰速较向上运动平均峰速降低大约20%,而其余方位无明显差异.结论 垂直扫视运动检查具有较好的可重复性和稳定性,可以用作上斜肌麻痹的定量检查.     

先天性上斜肌麻痹下斜肌的CT三维重建

目的：探索应用CT三维重建技术立体观察下斜肌形态的可行性。 方法：临床诊断单眼先天性上斜肌麻痹的患者29例进行眼眶CT扫描。用Mimics软件对原始CT扫描数据进行三维重建,建立基于个体CT扫描数据的下斜肌数字图像,观察双眼下斜肌的3D形态。用自身对照设计,比较麻痹眼和健眼下斜肌最大横径差异,设定P〈0.05为具有统计学意义。 结果：先天性上斜肌麻痹患者麻痹眼的下斜肌有的比健眼下斜肌粗;有的比健眼下斜肌细。下斜肌最大横径的测量：麻痹眼下斜肌最大横径平均为6.797依1.083 mm;健眼下斜肌最大横径平均为6.507依0.848 mm;两者的差异不明显,无统计学意义（P〉0.05）。 结论：基于CT扫描数据的下斜肌三维重建数字图像可以用于观察下斜肌的形态。     

先天性上斜肌麻痹患者二次手术的临床研究

目的 探讨先天性上斜肌麻痹患者二次手术的原因及治疗效果.方法 对12例首次行下斜肌减弱术,术后出现欠矫的先天性上斜肌麻痹患者行下斜肌探查术和下斜肌二次减弱术.根据术中探查结果对二次手术的原因进行分析,并对手术前后的眼位、眼球运动、代偿头位、Bielschowsky征等评价指标进行比较分析.结果 12眼探查术中:发现4眼下斜肌断端与renon囊等组织包裹在一起,形成了连接;3眼下斜肌断端附着于眼球颞下方巩膜上;3眼有残留下斜肌肌束;2眼下斜肌后徙位置较常规后徙位置偏颞下方.术后随访1a,1例患者33 cm垂直斜视度2△,其余11例患者33 cm正位,所有患者6 m正位,患眼下斜肌无亢进,Bielschowsky征为(-),无异常头位,与术前相比差异均有统计学意义,治愈率100％.3例下斜肌肌束残留患者首次行下斜肌减弱术后出现欠矫时间(平均18d)与其余9例患者(平均1.06 a)相比缩短,差异有统计学意义(Z=2.593,P=0.009).结论 先天性上斜肌麻痹患者首次行下斜肌减弱术后出现的欠矫可表现为类似上斜肌麻痹的症状,通过下斜肌探查术可以明确病因,针对病因采取恰当的下斜肌二次减弱术可以获得较好的手术效果.     

32例双侧先天性上斜肌麻痹的临床分析

目的：了解先天性上斜肌麻痹的临床特征。方法：对32例双侧先天性上斜肌麻痹进行临床分析。结果：①26例（81.3%)伴有垂直斜视,6例（18.7%)无垂直斜视,有垂直斜视者中12例（46.2%)伴有交替上斜视;②32例伴有V-型斜视;③32例双侧Bielschowsky征阳性;④32例均有不同程度的下斜肌功能亢进及上斜肌功能不足。结论：当临床上患者有交替上斜视、伴有V-型斜视、及下斜肌功能亢进及上斜股功能不足、双侧Bielschowsky征阳性时,应诊断双侧先天性上斜肌麻痹。     

下斜肌部分切除术治疗先天性上斜肌麻痹

目的探讨下斜肌部分切除术治疗先天性上斜肌麻痹的效果。方法观察17例接受下斜肌部分切除术治疗的先天性上斜肌麻痹术前术后9方位眼位，歪头试验及代偿头位的变化。结果垂直眼位变化小于15^△的先天性上斜肌麻痹患者术后眼位及代偿头位均恢复，大于15^△的仍残留部分眼位异常及代偿头位。结论下斜肌部分切除术对垂直眼位变化小于15^△的先天性上斜肌麻痹有效。     

先天性上斜肌麻痹患者28例术后双眼视功能变化

目的:探讨先天性上斜肌麻痹患者手术后双眼视功能变化。方法:先天性上斜肌麻痹患者28例手术前、后分别行斜视度和双眼视功能检查,统计分析其变化。结果:术后正位率89.3%。手术后有同时视、融合和立体视的患者分别增加9,13和13例,与术前相比差异具有显著性(P<0.05)。近立体视觉有明显改善。术前斜视度小、视力好且有融合功能的患者术后双眼视功能恢复好。结论:先天性上斜肌麻痹手术治疗在改善眼位的同时,双眼视功能部分得以重建。视功能恢复与视力、斜视度及有无融合功能有关。     

先天性上斜肌麻痹上斜肌肌腱病变程度的观察

目的:测量先天性上斜肌麻痹患者的上斜肌肌腱异常的程度。方法:采用临床横断面研究,自身配对对照设计。在给22例合并单眼上斜肌麻痹的内斜视(先天性内斜视、基本型内斜视、部分调节性内斜视)患者做双眼内直肌后退和上斜肌折叠等相应的垂直肌手术时,测量了患者的麻痹眼和非麻痹眼的上斜肌肌腱宽度和上斜肌肌腱紧张度。上斜肌紧张度用斜视钩垂直勾出前段上斜肌肌腱,肌腱离开巩膜的最大距离代表。结果:麻痹眼的上斜肌肌腱平均宽度为2.64±0.69mm,非麻痹眼的上斜肌肌腱平均宽度为3.84±0.56mm,两者的差异具有统计学意义(P<0.01);麻痹眼的上斜肌肌腱平均紧张度为9.02±1.68mm,非麻痹眼的上斜肌肌腱平均紧张度为6.48±1.33mm,两者的差异具有统计学意义(P<0.01)。结论:上斜肌麻痹时上斜肌肌腱相对较细、较松弛。     

A new classification of superior oblique palsy based on congenital variations in the tendon.

BACKGROUND: Superior oblique palsy is the most frequent isolated cranial nerve palsy seen in strabismus practice. It is traditionally diagnosed according to etiology as acquired, congenital, or idiopathic, but surgical treatment is based on deviation not etiology. Observations at surgery led to speculation that the superior oblique tendon is different in congenital compared with acquired superior oblique palsy and that this difference should be considered in surgical treatment. METHODS: The authors reviewed the charts of 82 patients (89 eyes) undergoing surgery on the superior oblique tendon for superior oblique palsy. In each case, the palsy had been diagnosed preoperatively as acquired, congenital, or idiopathic, and, at surgery, characteristics of the tendon anatomy were described. RESULTS: Thirty-eight superior oblique tendons (36 patients), diagnosed as congenital superior oblique palsy, included 33 abnormal tendons and 5 normal tendons. Twenty-four tendons (21 patients), diagnosed as traumatic superior oblique palsy, included 22 normal and 2 abnormal tendons. Twenty-seven tendons (25 patients), diagnosed as idiopathic, included 19 normal and 8 abnormal tendons. Abnormal tendons were divided into 4 categories: (1) redundant, (2) misdirected, (3) inserted in posterior Tenon's capsule, and (4) absent. CONCLUSIONS: The authors conclude that congenital superior oblique palsy is usually associated with a structural abnormality of the superior oblique tendon (87%). Whereas acquired superior oblique palsy usually has a normal tendon (92%). Superior oblique underaction in acquired superior oblique palsy results from a neural deficit. Potential variance in anatomy of the superior oblique tendon should be considered when undertaking surgery for superior oblique palsy.     

Trochlear nerve palsy following minor head trauma. A sign of structural disorder

Trauma-induced superior oblique palsy usually results from contusion or avulsion of the trochlear nerve or from decompensation of a congenital trochlear nerve palsy. Severe craniocerebral trauma is often associated with the former mechanism, whereas more minor closed-head injuries can decompensate a congenital phoria. We report a patient who developed an isolated trochlear nerve palsy following minor head trauma. Investigation revealed an unsuspected tentorial vascular malformation that was compressing the trochlear nerve in its subarachnoid course. In the absence of other features (e.g., documentation of old head tilt, large vertical fusion amplitudes) that support decompensation of a congenital phoria, compressive lesions should be sought in cases of fourth cranial nerve palsies that follow minor head trauma.     

Spontaneous consecutive Brown syndrome following superior oblique palsy

A 28-year-old female presented with a left trochlear nerve palsy, after indirect head trauma, with no fracture or orbital lesion. She had diplopia, a hypertropia and excyclotropia on right downgaze. Three months later the trochlear palsy had been replaced by Brown's syndrome: a deficit of elevation in adduction, with diplopia, incyclotropia and hypertropia in up-gaze. The Brown syndrome remained the same over a period of 18 months. A 31-year-old male suffered from severe brain contusion with intracerebral haemorrhage and bilateral trochlear nerve palsy. Three years later, he had a bilateral trochlear palsy with bilateral severe Brown's syndrome, with a right hypertropia and 10° to 25° incyclotropia in upgaze and 5° to 10° excyclotropia in downgaze. The field of binocular vision was shifted to left gaze. Orbital CT scan was normal. At surgery, the forced duction test was positive for Brown's syndrome on both sides and the tendon of the superior oblique muscle of the right eye was thickened. The field of binocular vision was centralized after surgery but torsional diplopia in upgaze and downgaze was present as before. Secondary Brown's syndrome after (persisting or vanishing) trochlear nerve palsy without any direct trauma to the superior oblique muscles or the orbit could be caused by a fibrotic reaction of the superior oblique tendon or adjacent structures. This could be due to inactivity or to indirect trauma.     

Comparison of Muscle Volume Between Congenital and Acquired Superior Oblique Palsies by Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) studies of superior oblique (SO) muscles have revealed a high incidence of SO muscle atrophy/hypoplasia in congenital SO palsy patients. It has also been reported that long-standing acquired SO palsy patients show atrophic SO muscles in the affected eye. The purpose of this study was to compare the incidence of SO muscle atrophy/hypoplasia in congenital and acquired SO palsy by utilizing MRI. Coronal MRI image planes were taken from 29 cases of unilateral congenital SO palsy and 9 cases of acquired unilateral SO palsy patients. The SO muscle bellies were traced and their sizes were measured from each image plane. The total volume of the affected superior oblique muscle was compared with that of the normal fellow eye. The mean volume of the affected superior oblique muscle to that of the normal muscle was 45.3% (SD = 30.1) in the congenital group and 65.8% (SD = 22.7) in the acquired group. The volume reduction of the SO muscle in congenital SO palsy patients appears to be mainly a congenital abnormality rather than a secondary change, as seen in acquired SO palsy patients.     

ARIX gene polymorphisms in patients with congenital superior oblique muscle palsy

AIM: To identify ARIX gene polymorphisms in patients with congenital superior oblique muscle palsy and to find the relation between the ARIX gene and congenital superior oblique muscle palsy. METHODS: The three exons of the ARIX gene were sequenced by genomic DNA amplification with polymerase chain reaction (PCR) and direct sequencing in 15 patients with superior oblique muscle palsy (13 with congenital and two with acquired palsy) and 54 normal individuals. PCR products cloned into plasmids were also sequenced. A family with father and a daughter each having congenital superior oblique muscle palsy was also involved in this study. RESULTS: Four patients with congenital superior oblique muscle palsy carried heterozygous nucleotide changes in the ARIX gene. One patient with the absence of the superior oblique muscle had T7C in the 5'-UTR of the exon 1 and C-44A in the promoter region, both of which were located on the same strand. Another unrelated patient with congenital superior oblique muscle palsy had C76G in the 5'-UTR of the exon 1 and C-9A in the promoter region on the same strand. G153A in the 5'-UTR of exon 1 was found in common in two affected members of a family with congenital superior oblique muscle palsy. This G153A in the 5'-UTR of exon 1 was also present in four unrelated normal individuals. No other heterozygous nucleotide changes were found in normal individuals. CONCLUSIONS: The nucleotide change (G153A) in the 5'-UTR of exon 1 co-segregated with congenital superior oblique muscle palsy in one family. Four other nucleotide changes in the exon 1 or the promoter region were found only in patients with congenital superior oblique muscle palsy. These nucleotide polymorphisms may be one of the risk factors for the development of congenital superior oblique muscle palsy.     

Vascular compression as a cause of superior oblique myokymia disclosed by thin-slice magnetic resonance imaging

PURPOSE: To describe a case of superior oblique myokymia in which thin-slice magnetic resonance imaging (MRI) appeared to show vascular compression of the trochlear nerve. METHODS: A 50-year-old woman presented with episodic monocular oscillopsia. Neuro-ophthalmologic examinations showed intermittent intorsional microtremor of her right eye, diagnosed as right superior oblique myokymia. Thin-slice (1.6 mm) MRI, using spoiled gradient recalled acquisition in the steady state, was employed to examine the trochlear nerve in its course through the ambient cistern. RESULTS: Imaging disclosed a branch of the posterior cerebral artery immediately adjacent to the right trochlear nerve. CONCLUSION: These magnetic resonance findings suggest that a cause of superior oblique myokymia may be vascular compression of the trunk of the trochlear nerve.     

Trochlear Palsies Caused by Isolated Trochlear Schwannomas

Purpose: To describe clinical features and management of 4 patients suffering from unilateral superior oblique palsies due to MRI-documented trochlear nerve schwannomas.

Methods: Chart reviews of 4 patients seen at the departments of ophthalmogy and neurology at the University of Mainz.

Results: All four patients were male, aged 36 to 72 years at initial presentation. None suffered from neurofibromatosis. The history of double vision prior presentation was 9 months to 13 years, follow-up time was 9 to 156 months. Two patients didn’t receive any intervention: one remained stable over the follow-up time of 9 months. In patient #2, fourth nerve palsy was diagnosed 13 years prior to confirmation of a trochlear schwannoma by high-resolution MRI. In the third patient disturbing diplopia and head tilt were sufficiently corrected by strabismus surgery (combined oblique muscle surgery). The fourth patient had received stereotactic radiotherapy of an 8 mm schwannoma. He remained unchanged in the orthoptic measurements for 3,5 years. None of these patients developed any additional symptoms or signs of further cranial nerve or central nervous system involvement.

Conclusion: A trochlear nerve schwannoma is a possible cause of an isolated unilateral superior oblique palsy. MRI is a helpful tool for diagnosis and follow-up. Conservative management seems to be justified as patients can remain unchanged over years.     

Central trochlear palsy

Historically, the trochlear (IV) nerve has been "neglected" by neurologists and ophthalmologists. However, the reported incidence of trochlear palsy in two large series has more than doubled in the past two decades, indicating increasing awareness of this nerve. Trauma is the most common cause of trochlear palsy, as the trochlear nerve is anatomically more vulnerable to trauma than the other ocular motor nerves. Trochlear palsy can also be caused by vascular and inflammatory diseases, congenital factors, toxic substances and tumors. Diplopia secondary to vertical and horizontal deviation is the most common presentation. The trochlear nerve has a relatively high recovery rate after the underlying cause of injury has been corrected. In this article, the anatomy and physiology of the trochlear nerve are described, and the various etiologies, methods of diagnosis and differential diagnosis of trochlear palsy are reviewed.     

Abnormalities of the oculomotor nerve in congenital fibrosis of the extraocular muscles and congenital oculomotor palsy

PURPOSE: High-resolution magnetic resonance imaging (MRI) can now directly demonstrate innervation to extraocular muscles and quantify optic nerve size. A quantitative MRI technique was developed to study the oculomotor nerve (CN3) and applied to congenital fibrosis of extraocular muscles (CFEOM) and congenital oculomotor palsy. METHODS: The subarachnoid portions of the CN3s were imaged with a 1.5-T MRI scanner and conventional head coils, acquiring heavily T(2)-weighted oblique axial planes 1-mm thick and parallel to the optic chiasm. Thirteen normal subjects, 14 with CFEOM, and 3 with congenital CN3 palsy were included. Digital image analysis was used to measure CN3 diameter, which was correlated with motility findings. RESULTS: In CFEOM, CN3 diameter was bilaterally subnormal in eight subjects, unilaterally subnormal in three subjects, and normal in three subjects. Mean +/- SD CN3 diameter in CFEOM was 1.14 +/- 0.61 mm, significantly smaller than the diameter in normal subjects, which measured 2.01 +/- 0.36 mm (P < 0.001). CN3 diameter variably correlated with clinical function. One subject with congenital CN3 palsy showed bilateral CN3 hypoplasia, but CN3 diameter was normal in two other subjects with congenital CN3 palsy. CONCLUSIONS: Unilateral or bilateral hypoplasia of CN3 is quantitatively demonstrable using MRI in many cases of CFEOM and occasionally in congenital CN3 palsy. Variations in CN3 diameter in CFEOM and congenital CN3 palsy suggest mechanistic heterogeneity of these disorders that may be clarified by further imaging and genetic studies.     

Paralytic strabismus

In the last year, published works on paralytic strabismus have concerned many topics. New advances have been made in the knowledge of epidemiology of ocular nerve palsies in children, muscular causes of paralytic strabismus, and neuroimaging management of patients with third nerve palsy who are at risk of cerebral aneurysms. The author describes reports on rare associations of oculomotor imbalances and neurologic diseases as well as atypical orbital localizations of tumors. He also discuss new neuroimaging findings in congenital superior oblique muscle palsy and new acquisitions on cyclofusion deterioration in acquired trochlear palsy.