Recurrent isolated abducens nerve palsy – unusual manifestation of a known syndrome: Report of two cases
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.193807
Source of Support: None, Conflict of Interest: None
Abducens nerve has the longest intracranial course after emerging at the pontomedullary sulcus in the caudal pons. It is vulnerable to compression owing to its points of fixation along its course, its tortuosity, and its attachment to the skull base. Following are the etiologies of abducens nerve palsy: Idiopathic (8–30%), ischemic (0–36%), traumatic (3–30%), aneurysmal compression (0–6%), and miscellaneous (10–30%). Microvascular cause is the most common attributable cause for an acute isolated ocular motor mononeuropathy. Non-microvascular causes such as neoplasms and inflammation should be considered in cases of isolated relapsing-remitting abducens nerve palsies. Here, we report two patients who presented with isolated relapsing-remitting abducens nerve palsies. The first patient had primary Sjőgren's syndrome (SS) and the second patient had idiopathic intracranial hypertension (IIH). Primary SS and IIH presenting as isolated relapsing-remitting abducens nerve palsy have not been reported.
A 44-year-old lady presented with a history of throbbing pain in the right periorbital region radiating to the right frontotemporal region of 1-week duration. This was followed by double vision lasting for two days mainly in the primary position of the eye and also towards the right lateral gaze that disappeared on closing one eye. There was no redness of eyes, proptosis, fever, or vomiting. She did not have any other comorbidities. Two months prior to the present symptomatology, she had similar symptoms of pain in the right periorbital region radiating to the right frontotemporal region along with double vision. She was diagnosed to be having a right lateral rectus weakness due to right abducens nerve palsy and was treated with oral prednisolone for 2 weeks. She had symptomatic improvement following which the steroids were tapered and stopped. Neurologically, she was conscious and oriented. There was esotropia of the right eye with impaired abduction suggestive of right lateral rectus palsy. Other cranial nerves were normal. There were no other abnormalities on neurological examination. A clinical diagnosis of recurrent right abducens nerve palsy was made. Magnetic resonance images (MRI) of the brain with gadolinium enhancement did not reveal abducens nerve or meningeal enhancement. Cerebrospinal fluid (CSF) analysis showed a normal opening pressure, protein 72 mg/dL, cell count 3 cells/mm 3 (lymphocytes), and no malignant cells. Complete hemogram showed an elevated erythrocyte sedimentation rate (ESR; 35 mm/h). The renal, hepatic, and thyroid function tests were normal. Plasma glycated haemoglobin was normal. Serum antinuclear, anti-SS-A, and SS-B antibodies were positive. Serological testing for human immunodeficiency virus (HIV) and hepatitis B and C were negative. Schirmer's test to assess the adequacy of lacrimal secretions was positive (5 mm of tear flow over 5 min). On further questioning, the patient did not report any history of dry eyes or mouth. Lip biopsy showed aggregated foci of lymphocytes in the minor salivary glands [Figure 1], [Figure 2], [Figure 3]. She was started on oral steroids (1 mg/kg/day) with azathioprine (2 mg/kg/day). At follow-up after 8 weeks, there was significant improvement in her symptomatology with amelioration of the lateral rectus palsy. She remains asymptomatic at subsequent follow-up conducted every 3 months for 2 years.
A 36-year-old male patient presented with a history of double vision of 2-day duration mainly on primary position and looking towards the left lateral gaze. The diplopia disappeared on closing one eye. There was no redness of eyes, proptosis, blurring of vision, fever, or headache. He did not have any other comorbidity. Previously, he had 2 similar episodes; one 4 years ago and another 2 years ago. On both the occasions, he had painless binocular double vision in the left lateral gaze. Brain MRI with gadolinium enhancement was normal. He was treated as a case having a left abducens nerve palsy in another hospital with oral steroids and improved completely. Neurologically, he was conscious and oriented. Fundus examination showed blurring of the nasal disc margin of both the eyes. Pupils were equal and reactive. There was esotropia of the left eye with impaired abduction suggestive of left lateral rectus palsy. Other cranial nerves were normal. A clinical diagnosis of recurrent left abducens nerve palsy was made. Complete hemogram and renal, hepatic, and thyroid function tests were normal. Plasma glycated hemoglobin was normal. Serum antinuclear antibodies were negative. Serological testing for HIV, hepatitis B surface antigen, and Venereal Disease Research Laboratory test were negative. Brain MRI with gadolinium enhancement did not reveal abducens nerve or meningeal enhancement. MR venography was normal. CSF pressure was high (390 mm of CSF) with normal protein, glucose, and cell count. A diagnosis of isolated relapsing-remitting sixth nerve palsy without headache due to IIH was made. He was treated with acetazolamide and oral glycerol. Visual field charting showed concentric constriction of the visual fields in both the eyes. He was referred to an ophthalmologist for optic nerve fenestration. There was improvement in lateral rectus function at a 3-month follow-up.
Isolated abducens nerve palsy in young individuals should be evaluated with neuroimaging to rule out meningeal infiltrative and metastatic processes. Isolated abducens nerve palsy in adults more than 50 years of age are usually ischemic if there are associated vascular risk factors such as diabetes mellitus, hypertension, or dyslipidemia. Usually, isolated ischemic abducens nerve palsy returns to normality within 3 months. Persistent abnormality beyond 3 months require investigations to determine the presence of other etiologies, such as infective and inflammatory causes, namely, syphilis, collagen vascular disease, and sarcoidosis., Following are the causes for recurrent isolated ischemic abducens nerve palsy: Aneurysm, vasculopathy, sphenoiditis, metastases and tumors like a parasellar/petrous apex meningioma.
The neurological involvement in primary SS ranges from peripheral nerve (10–20%) to cranial nerve and central nervous system involvement (1.5 to 20%). The first patient was diagnosed to be having a primary SS, which caused recurrent cranial mononeuropathy but sicca symptoms or systemic manifestations were absent. Patient had positive anti-SS-A and SS-B antibodies, diagnostic histopathological features in salivary gland biopsy, and a positive Schirmer's test. Three out of 6 criteria set by European Community Study (ECS) group for the diagnosis of primary SS were, therefore, fulfilled.
The absence of xerostomia or xerophthalmia does not exclude the diagnosis of SS. Delalande et al., reported that 38% patients had sicca symptoms before, 15% patients had these symtoms at the same time, whereas 47% patients had these symptoms after the onset of neurologic features. The exact pathomechanisms underlying the cranial neuropathy in SS are largely unknown. Vasculitis in small arteries and arterioles with subsequent development of an axonopathy is the postulated mechanism for multiple cranial neuropathies, except for trigeminal neuropathy, which is due to ganglionopathy/ganglionitis.
There are only a few reports on the isolated cranial mononeuropathy caused by SS. Galbussera et al., reported a case of isolated oculomotor nerve palsy related to SS. Lui et al., reported a patient with isolated oculomotor nerve palsy due to SS showing rapid and almost complete recovery after 2 months of corticosteroid and azathioprine treatment. Chu et al., reported a patient with isolated trochlear nerve palsy due to SS. Isolated abducens nerve palsy due to SS has not been reported.
IIH presenting as isolated relapsing-remitting sixth nerve palsy without headache has not been reported. IIH is a syndrome in which there is increased intracranial pressure (ICP) of an unknown cause. Revised modified Dandy criteria is used to define the syndrome: (1) Symptoms and signs of raised ICP (headache, nausea, vomiting, pulsatile tinnitus, transient visual obscurations, and papilledema); (2) no localizing signs, except for abducens nerve palsy; (3) no cause for raised ICP identified on neuroimaging (brain MRI); (4) CSF opening pressure of greater than 25 cmH2O, with normal CSF composition; and (5) no alternate explanation for the raised ICP. Headache is the most common symptom at presentation and is typically holocranial, worse after waking up. Papilledema is the most common sign at presentation. Untreated papilledema results in progressive irreversible visual loss and secondary optic atrophy. The patients may have binocular horizontal diplopia due to unilateral or bilateral abducens nerve palsy. Vertical diplopia, due to third nerve palsy, fourth nerve palsy, or skew deviation, has been rarely reported in patients with a high CSF opening pressure.
The present case series depicts two different etiologies for isolated relapsing-remitting abducens nerve palsy in middle aged patients. Both etiologies are known syndromes but the presenting manifestations in these patients were unusual. Primary SS should be considered in patients with recurrent cranial mononeuropathy even in the absence of sicca symptoms. Measurement of CSF opening pressure should be done in patients with recurrent isolated abducens nerve palsy to rule out IIH.
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[Figure 1], [Figure 2], [Figure 3]