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Show ORIGINAL CONTRIBUTION Isolated Acquired Unilateral Horizontal Gaze Paresis from a Putative Lesion of the Abducens Nucleus Neil R. Miller, MD, Valerie Biousse, MD, Thomas Hwang, MD, Saurabh Patel, MD, Nancy J. Newman, MD, and David S. Zee, MD In three patients, acute horizontal gaze pareses developed that could not be overcome with the oculocephalic maneuver, indicating a putative lesion of the ipsilateral abducens nerve nucleus. None of the patients had a facial nerve paresis or evidence of a trigeminal sensory neuropathy. Although most lesions that affect the abducens nerve nucleus also damage the ipsilateral fasciculus of the facial nerve, small lesions in this region can produce an isolated horizontal gaze paresis. ( JNeuro- Ophthalmol 2002; 22: 204- 207) Small lesions affecting the abducens nucleus cause ipsilateral gaze palsy for both voluntary and reflex- induced movements. The gaze palsy is typically associated with ipsilateral peripheral facial palsy caused by damage to the adjacent facial nerve fascicle that loops around the abducens nucleus ( 1- 3). We report two patients in whom acute horizontal gaze pareses developed, unassociated with ipsilateral facial weakness or evidence of any other cranial neuropathy. CASE REPORTS Case 1 A 57- year- old woman with a history of acute intermittent porphyria, taking no medications was visually well until May 2001, when she experienced a tight sensation behind both eyes and noted that she could see clearly only when she turned her head to the left. Shortly thereafter, a friend told her that she seemed to be having difficulty moving her eyes. She was then evaluated at the Wilmer Eye Institute of the Johns Hopkins Hospital. On initial examination, the patient's visual acuity was 20/ 20 OU, with normal color vision by pseudoisochromatic Wilmer Eye Institute ( NRM, TH, SP, DSZ) and the Department of Neurology ( NRM, DSZ), the Johns Hopkins Hospital, Baltimore, Maryland, and the Departments of Ophthalmology ( VB, NJN), Neurology ( VB, NJN), Neurosurgery ( NJN), Emory University School of Medicine, Atlanta, Georgia. Address correspondence to Neil R. Miller, MD, Maumenee B- 109, Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, MD 21287, USA; E- mail: nrmiller@ jhmi. edu plates and normal visual fields by automated perimetry. The pupils were isocoric and normally reactive to light and near stimulation. There was no ptosis and no proptosis. The patient had a left face turn, and her eyes were deviated to the right. She could not voluntarily move them out of rightward gaze, nor was there any improvement in movement with the oculocephalic maneuver. Her vertical gaze was intact. Optokinetic stimulation produced normal saccades when the drum was rotated to the patient's left, but there were no saccades with rotation of the drum to the patient's right. There was no evidence of facial weakness on either side, and facial sensation was normal bilaterally. A lesion of the left abducens nucleus was suspected, and the patient underwent thin- section magnetic resonance imaging ( MRI), including diffusion- weighted images, showing no lesions. She then underwent a lumbar puncture that showed no abnormalities, and several serologic studies whose results were negative, including a complete blood count and differential, an erythrocyte sedimentation rate, an assay for angiotensin- converting enzyme, a serologic test for syphilis, Lyme titers, and assays for antinuclear, antiGQlb, antiphospholipid, and fluorescent treponemal antibodies. One week after the onset of symptoms, the patient underwent quantitative assessment of ocular motility. At this time, she still had a face turn to the left, but it was not as marked as in the initial evaluation. She was now able to move her eyes to the left but still not to midline ( Fig. 1). Saccades to the right were normal with respect to both amplitude and velocity, but saccades to the left were hypomet-ric and showed reduced velocities; convergence was intact ( Fig. 2). The findings were thought to be most consistent with a lesion of the left abducens nucleus. The patient was monitored at regular intervals. One month after the onset of symptoms, she could move her eyes to the midline, and 2 months after the onset of symptoms, her ocular motility had returned to normal. Case 2 A 57- year- old man was referred to the Neuro- Ophthalmology Unit at Emory University for evaluation of ^ 204. POL lp. l097/ 01. WNQ. gnn0028867.9267n. 3A . JNeuro- Ophthalmol Vol 22, No. 3,2Q02 , Copyright © Lip pincott Williams & Wifkins. Unauthorized reproduction of this article is prohibited. HORIZONTAL GAZE PARESIS AND ABDUCENS NUCLEUS LESION JNeuro- Ophthalmol, Vol 22, No. 3, 2002 FIG. 1. Case 1: right gaze is normal ( left), but on attempted left gaze, the eyes do not move beyond midline ( right). diplopia after embolization of a basilar tip aneurysm. His medical history was remarkable for systemic hypertension and diabetes mellitus type 2. Eighteen days earlier, he had experienced a sudden, severe headache associated with a stiff neck and had been found to have evidence of a subarachnoid hemorrhage. A cerebral angiogram had revealed a basilar tip aneurysm, and the patient had undergone aneurysm embolization using detachable platinum coils. Immediately afterwards, the patient experienced diplopia and intermittent dizziness associated with a sensation of falling to the left. The patient's visual acuity and visual fields were normal. The pupils were isocoric and normally reactive to light and near stimulation. The patient had full vertical eye movements and full left gaze in both eyes. He had complete absence of right gaze for both saccades and pursuit ( Fig. 3). Ocular motility did not improve with the oculocephalic maneuver. In primary position distance viewing, he had a 25- prism diopter left hypertropia and a 10- prism diopter esotropia. He also had upbeat nystagmus with a counterclockwise torsional component. The results of the remainder of RIGHTWARD SACCADES LEFTWARD SACCADES 500 1000 1500 2000 2500 3000 3500 U 500 1000 1500 2000 2500 3000 3500 500 1000 1500 2000 2500 3000 3500 t- A- 500 1000 1500 2000 2500 3000 3500 1 500 1000 1500 2000 2500 3000 3500 J . l( K REVEL _ 100I - 20o[ " V v~ 500 1000 1500 2000 2500 3000 3500 500 1000 1500 2000 2500 3000 3500 100. LEVEL .1001 - 2001 B - H- " V-\ r 500 1000 1500 2000 2500 3000 3500 c Time ( seconds) FIG. 2. Case 1: quantitative eye movement recordings. A: Right gaze. Saccades have a normal amplitude and velocity ( arrowhead). REPOS, OD position; REVEL, OD velocity; LEPOS, OS position; LEVOS, OS velocity. Position is measured in degrees from center; velocity is measured in degrees/ second; time is measured in milliseconds. B: Left gaze. Saccades have reduced amplitude and decreased velocity ( arrowhead). REPOS, OD position; REVEL, OD velocity; LEPOS, OS position; LEVOS, OS velocity. C: Convergence. Both eyes adduct normally, including the OD, which did not adduct ( move to the left) on attempted versions. RE, OD position; LE, OS position. 205 Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited JNeuro- Ophthalmol, Vol. 22, No. 3, 2002 Miller et al. FIG. 3. Case 2: eye movements. Note absence of dextroversion. his cranial nerve examination were unremarkable. He had normal facial strength and no evidence of a trigeminal sensory or motor neuropathy. Ophthalmoscopic examination revealed bilateral optic disc swelling but no evidence of intraocular hemorrhage. Thin- section MRI revealed no lesions. Within 1 month, his disc swelling had resolved and his ocular motility had begun to improve. Case 3 A 4- year- old African- American girl was referred to the Neuro- Ophthalmology Unit at Emory University for evaluation of abnormal eye movements. Her medical history was unremarkable. She had been the product of a full-term pregnancy and normal vaginal delivery, and her development had been normal. Her mother had had a cerebral infarction at 32 years of age. Two days before she visited our unit, the child's parents noticed that she was looking to the right with her face turned to the left. They also noted that she had become sleepy and abnormally quiet. The patient's visual acuity and confrontation visual fields were normal. Her pupils were isocoric and normally reactive to light and near stimulation. The patient had full vertical eye movements and full right gaze in both eyes. She had complete absence of left gaze for both saccades and pursuit. Ocular motility did not improve with the oculo-cephalic maneuver. In primary position for distance viewing, she was orthophoria The results of the remainder of her cranial nerve examination were unremarkable. She had normal facial strength. The results of ophthalmoscopic examination were normal. The results of general and neurologic examinations were otherwise unremarkable. Thin- section MRI revealed a small lesion in the pons in the region of the left abducens nerve nucleus ( Fig. 4). The patient's gaze improved spontaneously over the next few days, and no further evaluation was done. One month later, her ocular motility was normal. DISCUSSION Complete absence of unidirectional horizontal gaze for saccades, pursuit, and vestibulo- ocular reflexes localizes a lesion to the ipsilateral abducens nerve nucleus ( 1). Most cases of damage to this structure are associated with ipsilateral facial nerve paresis caused by damage to the facial nerve fascicle as it loops around the abducens nerve nucleus ( 2- 5). We believe our cases to be the first examples of abducens nuclear lesions causing a horizontal gaze paresis without an associated facial nerve paresis. Although the FIG. 4. Case 3: axial T2- weighted magnetic resonance imaging scan shows a small hyperintense lesion in the region of the left abducens nerve nucleus ( arrowhead). „ 206 , , „ . . , „ . . © 2002 Lippincott Williams & Wilkins , Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. HORIZONTAL GAZE PARESIS AND ABDUCENS NUCLEUS LESION JNeuro- Ophthalmol, Vol. 22, No. 3, 2002 MRIs were normal in two of our patients ( Patients 1 and 2), we believe it most likely that all of the causative lesions were ischemic. The first patient probably experienced a small hypoxic lesion, possibly related to her porphyria. Indeed, several authors have reported patients with acute intermittent porphyria who experienced transient ( 6) or permanent ( 7) blindness from ischemia thought to be vasospastic. The second patient probably had a small infarction from occlusion of a circumflex pontine perforating vessel during embolization. In the third patient, the MRI did show a small lesion, presumably ischemic, in the region of the abducens nerve nucleus ipsilateral to the gaze paresis. Many lesions of the brainstem that affect ocular motor structures cause neurologic deficits in addition to those affecting the ocular motor pathways, but small focal brainstem lesions can cause both complete and partial isolated oculomotor nerve pareses, trochlear nerve pareses, and abducens nerve paresis ( 8- 17). Our three cases provide evidence that small lesions can damage the abducens nerve nucleus without causing either trigeminal or facial neuropathies. REFERENCES 1. Porter JD, Baker RS. Anatomy and embryology of the ocular motor system. In MillerNR, NewmanNJ, eds. Walsh andHoyt's Clinical Neuro- Ophthalmology, 5th ed, Vol 1. Baltimore, Williams & Wilkins, 1998: 1043- 99. 2. Bronstein AM, Morris J, Du Boulay G, Gresty MA, et al. Abnormalities of horizontal gaze: clinical, oculographic and magnetic resonance imaging findings: I. Abducens palsy. J Neurol Neurosurg Psychiatry 1990; 53: 194- 9. 3. Bronstein AM, Rudge P, Gresty MA, et al. Abnormalities of horizontal gaze: clinical, oculographic and magnetic resonance imaging findings. II. Gaze palsy and internuclear ophthalmoplegia. J Neurol Neurosurg Psychiatry 1990; 53: 200- 7. 4. Miiri R, Chermann JF, Cohen L, et al. Ocular motor consequences of damage to the abducens nucleus area in humans. J Neuroophthal-mol 1996; 16: 191- 5. 5. 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