1 서울대학교 의과대학 신경외과학교실, 2 서울대보라매병원 신경외과, 3 서울대보라매병원 안과
김동환
1, 박성배
2, 정호경
3, 양희진
21 Department of Neurosurgery, Seoul National University College of Medicine, Seoul, Korea
2 Department of Neurosurgery, Seoul National University Boramae Hospital, Seoul, Korea
3 Department of Ophthalmology, Seoul National University Boramae Hospital, Seoul, Korea
Dong Hwan Kim, MD
1, Sung Bae Park, MD
2, Ho Kyung Choung, MD
3, Hee-Jin Yang, MD
2A Case of Traumatic Oculomotor Nerve Palsy Diagnosed by Thin Slice MR Imaging
- Running Head : III CN palsy on thin slice MRI -
J Korean Skull Base Society 8권 1호 : 17~22, 2013
Cranial nerve palsies are common consequences of trauma, among which oculomotor nerve involvement is relatively common. Although it is clinically evident due to disturbance in extraocular movement, imaging diagnosis of traumatic oculomotor nerve palsy is not easy.
We report a case of traumatic oculomotor nerve palsy diagnosed by high resolution thin- slice magnetic resonance imaging (MRI). A 31-year-old female was brought to emergency room after fall down injury. Left oculomotor palsy was detected on neurological examination, whereas brain CT showed no definite traumatic intracranial lesion. Brain MRI with thin slice imaging technique showed enhancement of cisternal segment of right oculomotor nerve without any abnormality in contour. This type of traumatic oculomotor nerve palsy, detected only by enhancement without any abnormality in contour, has not been reported. The oculomotor palsy improved slowly over during follow-up. This case shows thin-slice MR imaging is very useful for diagnosis of cranioneuropathy.
논문 접수일 : 2013년 4월 20일 심사 완료일 : 2013년 5월 20일 주소 : Department of Neurosurgery,
Boramae Hospital, Seoul National University
20, Boramae-ro 5-gil, Dognjak-gu, Seoul, Korea, 156-707
Tel : 82-2-870-2303 Fax : 82-2-870-3863 E-mail : [email protected]
Hee-Jin Yang, MD
교신저자
oculomotor nerve injury, MRI, high resolution, enhancement
Key Words
종설1 증례1 증례2 증례3 증례4 종설1
증례2
▒ Introduction
Oculomotor nerve injury related head trauma is relatively common.8)The oculomotor nerve is the motor nerve for the levator muscle of the upper eyelid, rectus superior muscle,
rectus medialis muscle, rectus inferior muscle, and inferior oblique muscle.11)The oculomotor nerve palsy is well recognized clinical syndrome, which results in ptosis, deviation of the eyeball outward, double vision, and a dilated pupi.l7) However, it has been difficult to identify the
Photographs of extraocular motions 1 week after trauma. There is ptosis on left side. The left eyeball is deviated laterally in straight forward gaze.
There are limitations of medial, upward, and downward gaze.
Fig. 1
Brain CT on initial evaluation. There is no definite abnormal finding in basal cistern or midbrain.
Fig. 2
oculomotor nerve reliably using radiological technique, even in conventional MR imaging due to small size and close proximity to other anatomical structures.14)Here we present one case of posttraumatic oculomotor nerve palsy detected by thin slice MR imaging and discuss its clinical implication.
▒ Case Report
A 31-year-old female was brought to emergency room after fall down injury. She was alert in mentality. On radiological evaluation, there were fractures at odontoid process(Type 2), scapula and ribs. Left oculomotor nerve
palsy was detected at initial evaluation. Increased size of left Pupil (6mm) with loss of light reflex, ptosis, and medial gaze limitation were observed (Figure 1). Computed tomography revealed no definite traumatic intracranial lesion such as skull fracture, intracranial hemorrhage, etc (Figure 2).
Odontoid fracture was managed by screw fixation, other fractures by conservative care. Brain MRI was checked 2 weeks after trauma using 3.0 tesla MRI (Achieva 3.0, Philips, Best, Netherlands). After acquisition of conventional T2 weighted images in axial and coronal plane, thin slice imaging was done for detection of cranial nerve lesions. The conditions for thin slice imaging were as follows: 3D T2
Magnetic Resonance Imaging (MRI) taken 2 weeks after trauma
A. Routine T2 weighted axial image shows no definite structure suggestive of oculomotor nerve.
B. Thin slice T1 axial image shows normal sized oculomotor nerves in prepontine cistern, although they are not so distinct.
C. Thin slice T2 axial image shows normal thickness oculomotor nerves more distinctly without any difference in contour.
D. The post contrast T1 weighted thin slice axial image shows prominent enhancement of left oculomotor nerve in comparison with that on right side.
Right oculomotor nerve is marked by, arrow, left oculomotor nerve by arrowhead.
A
C D
B Fig. 3
VISTA (Volumetric Isotropic T2 weighted Acquisition), T1 SE pre-contrast T1 weighted images, and 3D T1 TFE (Turbo Field Echo) WATS (Water Selective) with enhancement. The details of imaging parameters are described in Table 1. It was not possible to delineate oculomotor nerve on conventional MR imaging. Even in slice image there was no difference in left and right oculomotor nerve, although the nerves were disntinctly delineated. Contrast enhanced thin slice MRI showed enhancement of cisternal segment of left oculomotor nerve(Figure 3). No infectious, vascular or tumorous lesions were detected.
Her disturbance in extraocular motion recovered over time on follow-up evaluation 3 weeks after trauma (Figure 4). On last follow up 10 months after trauma she was in stable condition, with residual oculomotor nerve palsy, no definite further improvement compared to 3 weeks after trauma.
▒ Discussion
The oculomotor nerve has five segments: nuclear, intra- axial midbrain, cisternal, cavernous and intra-orbital(extra-
Photographs of extraocular motions 3 weeks after trauma. There are some improvements in lateral deviation of left eyeball and ptosis. It is notable for upward movement of left upper eyelid on medial gaze, compared to straight forward gaze, suggestive of aberrant regeneration. The fold of upper left eyelid on straight forward gaze (arrowhead) disappeared on right lateral gaze (arrow).
Fig. 4
3D T2 VISTA 2000 250 300X300 180X180 0.6
T1 SE pre-contrast
459 12 256X191 180X180 2.0
T1 WI
3D T1 TFE WATS
13 6.6 300X222 180X180 0.6
with enhancement
Image Sequence TR(ms*) TE(ms) Matrix FOV(mm) Slice thickness (mm)
Table 1. Parameters for high resolution thin slice MRI
FOV: field of view VISTA: Volumetric Isotropic T2 weighted Acquisition T1WI: T1 weighted image TFE WATS: Turbo Field Echo Water selective
* milliseconds
cranial) segments.11)In this case, cisternal segment of oculomotor nerve was involved. In the prepontine cistern, the nerve travels between the superior cerebellar and posterior cerebral arteries. It is located infero-lateral to the posterior communicating artery.4)
The mechanisms of third cranial nerve injury at cisternal segments might be direct or indirect. The cisternal segment of oculomotor nerve can be affected by tumors, infections, or inflammatory polyneuropathy.2, 10) Vascular contact with or compression on the cisternal segment of the oculomotor nerve has been reported in patients whose vascular lesion itself was asymptomatic. Oculomotor nerve palsy may be caused by trauma. Injury to the brain stem may damage the nuclear or fascicular portion, or injury to the more peripheral segment of the nerve may be caused by a fracture that extends to the superior orbital fissure or cavernous sinus.1, 7) It is suggested that ophthalmoplegia is caused by downward displacement of the brainstem at the time of impact which directly injured the pupillomotor fibers on the ventromedial surface of the third nerve at the posterior petroclinoid ligament.12)
Although clinically conspicuous, it is not easy to diagnose oculomotor palsy by imaging study; the causative lesion remains unknown in approximately one fourth. Although MRI has superiority for anatomic detail over CT, it is not easy to detect abnormal findings in conventional imaging technique.7, 15)With the advent of high resolution MR sequences it became possible to get more precise imaging on cranial nerves.3, 14) It has been demonstrated that abnormal thickness, compression by vascular lesions, avulsion of roots, hypoplasia of oculomotor nerve can be detected by MRI.2, 6, 9)
Our case has a unique feature compared to previously reported cases. The oculomotor nerve showed abnormal enhacement without any abnormality precontrast image even in thin-slice high resolution image. There are reported cases of root avulsion or abnormal contour of oculomotor nerve and enhancement in various diseases.2, 10)However, enhancement of oculomotor nerve in traumatic condition without any abnormality in precontrast image has not been reported yet.
It is known that cranial nerves show enhancement in optic neuropathy, inflammatory cranial nerve lesions.5) Enhancement of oculomotor nerve at cisternal segment is always abnormal, revealing underlying inflammatory or neoplastic process, not yet described in traumatic condition.10) Nerve enhancement suggests breakdown of the blood/nerve barrier associated with nerve degeneration and regeneration after traumatic stretching, and may be long-lasting up to 2 years after initial trauma.13)
The possibility of recovery depends on the anatomic lesion and not on the ophthalmologic findings in the acute phase.7) Our case showed relatively rapid initial improvement followed by steady state with residual deficit. It is plausible that complete injury involving avulsion of root or motor nucleus injury involving brain stem show poor functional recovery compared to incomplete injury preserving continuity of nerve involving peripheral segment. Therefore, proper imaging diagnosis for oculomotor nerve palsy for localization of pathology is required to assess the prognosis of functional recovery. Thin section MRI can be a great help to physicians in a variety of situations involving cranial nerves, as depicted in our case.
▒ Conclusion
Posttrumatic cranioneuropathy might be caused by brain stem lesion such as diffuse axonal injury or by direct impact on cranial nerve itself and so on. Differentiation of etiology is necessary for management of associated pathology and assessing prognosis. This case shows relatively rapid and good recovery of cranial nerve dysfunction. This case show thin-slice MRI imaging is very useful for diagnosis of cranioneuropathy.
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