Benign recurrent unilateral abducens nerve palsy G. J. Hankey Neurology Registrar, Department of Neurology, Royal Perth Hospital, WA.
Abstract: The recurrence of an isolated unilateral left abducens nerve palsy on five occasions over five years is described in an adult. No evidence ofany systemic or intracranial disorder has been identified. The aetiology remains uncertain and the clinical course is benign. The diagnosis of 'benign' abducens nerve palsy is one of exclusion and is made retrospectively after an adequate period of serial evaluations. (Aust NZ J Med 1990; 20: 173-174.) Key words: Abducens nerve palsy, recurrent, benign, adult.
The occurrence of horizontal diplopia in association with a unilateral defect of ocular abduction demands a careful neurological examination and search for relevant potential causes of an acquired abducens (sixth cranial) nerve palsy or pseudo-sixth palsy.' Sometimes the diagnosis remains elusive but with time and evolution of the disease process the situation usually becomes clear. I n 1967, Knox et a/., reported 12 children with isolated sixth (VI) nerve palsy in all but one of whom the VI nerve palsy resolved within ten weeks.* They termed this entity 'benign sixth nerve palsy' and speculated that it was due to a preceding viral illness, although a conclusive causal relationship was not demonstrated. In 1972, Barnett reported that benign VI nerve palsy may be recurrent3 (although Robertson et U I . ,inferred ~ this possibility in one of their cases). Since then several case reports have indicated that benign VI nerve palsies in children can be r e c ~ r r e n t . ~ - ' ~ This paper describes, for the first time, the occurrence of benign recurrent unilateral VI nerve palsy in an adult, illustrating that this clinical entity is not confined to children.
CASE REPORT A 41-year-old man presented in December 1987 following the onset of his fifth episode of paralysis of the left lateral rectus muscle. His history dated back to April 1982 when, at age 36, he developed an illness characterised by a slight headache, fever and shivering. Two days later he developed horizontal diplopia due to a left lateral rectus palsy. The left temporalis and masseter muscles were wasted and weak but the remainder of the neurological examination was normal. There was no evidence of myasthenia gravis. Cranial C T scan, with and without contrast, included views of the cavernous sinus and brainstem and was normal. T h e cerebrospinal fluid (CSI;) opening pressure and lahorarory examination was normal. 'The left lateral rectus palsy completely resolved within four months.
In November 1982 he experienced a recurrence of the left lateral rectus palsy which again recovered complerely after two months. In 1984 and 1986 two further episodes of mild horizontal diplopia occurred, each lasting only a few days. In December 1987 he developed an upper respiratory tract infection and five days later noted the acute onset ofhorizontal diplopia in the primary position of gaze, increasing with horizontal gaze to the left. He was otherwise asymptomatic. His past health has been excellent and his family history unremarkable. Abnormalities on examination were confined to the cranial nerves. A left lateral rectus palsy was present, caubing a left esotropia. Wasting and weakness of the left masseter and temporalis muscles were present. 'l'here was no muscle fatigability. Full recovery occurred after two months.
DISCUSSION During the last six years this patient experienced five discrete episodes of paralysis of the left lateral rectus muscle, lasting from several days to four months. Recovery from each episode was spontaneous and complete. On two occasions the episodes were preceded by a non-specific febrile illness. In between attacks, the patient has enjoyed good health. Recurrent unilateral abducens nerve palsy in isolation is an uncommon clinical syndrome which may present diagnostic difficulty. Possible aetiological explanations in the adult include: recurrent infection, either local (otitis media) or systemic (viral);J repeated arteriosclerotic ischaemic microinfarction of the nerve trunk in patients with diabetes mellitus and/or hypertension;' myasthenia gravi$ ophthalrnoplegic migraine; fluctuating intracranial hypertension; a pontine angioma; intermittent nerve compression by a cavernous sinus dural arteriovenous malformation (AVM); a carotid siphon aneurysm in the infraclinoid portion of the cavernous sinus; or a minor anatomical abnormality such as an aberrant anterior inferior cerebellar a ~ t e r y Isolated .~ abducens nerve
Corresporrderrce ro: Dr Graeme J. Hankey, Department of Clinical Neurosciences, Western General Hospital, Crewe Road, Edinburgh, Scotland,
UK EH4 2XU. BENIGN R E C U K R E N r C;NILAI'ERAL AHI)UCEKS NERVE PALSY
Aust K Z J bled 1990; 20
173
palsy could also represent the initial presentation of multiple sclerosis but this diagnosis would be inappropriate before other neurological symptoms and signs of demyelination developed. The long history over more than five years, the complete remissions and the negative clinical features and investigations in this case strongly support the diagnosis of benign recurrent unilateral abducens nerve palsy of uncertain aetiology. The unlikely possibility of an underlying dural AVM or pontine angioma exists but the patient has become Familiar with the spontaneous recovery from each of these episodes and does not wish to proceed further with an MRI examination nor assume the risk of vertebral angiography. The underlying pathophysiology of this entity of benign recurrent abducens nerve palsy is speculative. Abducens nerve palsies can occur in the setting of infection, having been described after herpes zoster ophthalmicus' ' and during the incubation period of varicella.'* A post-infectious (viral) aetiology is certainly suggested by those patients who have developed a VI nerve palsy following immunisatiohs for viral diseases9 and is also implied in those cases, including this patient, in whom palsies developed after systemic illnesses that seemed to be viral in If so, the pathological basis would probably be demyelination or a localised arteritis. Of the five episodes of lateral rectus underaction in this patient, two were preceded by a non-specific febrile illness but two (those in 1984 and 1986) lasted only days. It is difficult to explain the latter episodes in terms of post-viral demyelination or arteritis. Also, several of the recent reports of recurrent isolated VI nerve palsy in children have made a post-infectious aetiology difficult to accept as the most likely factor in all c a s e ~ . ~ ~Reinecke ~.''' and Thompson found no history of concurrent illness in any of the five children they presented and stressed the difficulty in identifying a clear cause for this disorder.s The long-standing left trigeminal motor palsy in this patient is difficult to ignore in this setting. The possibility of a restricted or partial developmental abnormality of the left lower pontine tegmentum, similar to the Mobius syndrome (congenital bi-facial and abducens palsies), exists but its relevance to this entity of recurrent .VI nerve palsy is speculative. The occurrence of a unilateral abducens nerve palsy in a child or adult is important to recognise because it may be the initial manifestation of a progressive intracranial process.
174
If so, it is usually associated with other neurological or systemic abnormalities and if not, such abnormalities usually appear within a few weeks or months. Serial neurological, ophthalmological and radiological (CT or MRI scan) examinations are therefore mandatory. If, with the passage of time, the abducens nerve palsy is the sole neurological abnormality and possible treatable causes have been carefully excluded then it is worthwhile to at least consider the diagnosis of 'benign' abducens nerve palsy so that the patient may be reassured of its favourable prognosis. The value of serial neuro-ophthalmological examinations in these cases is emphasised.
Acknowledgements This patient was under the care of Dr E. G . Stewart-Wynne, Neurologist, Royal Perth Hospital and Dr W. M. Carroll, Neurologist, Sir Charles Gairdner Hospital, Western Australia. Accepted for publication: 9 June 1989.
References I. Glaser JS. Neuro-ophthalmology. Hagerstown, Harper & Row, 1978. 2. Knox DL, Clark DB, Schuster FF. Benign VI nerve palsies in children. Pediatrics 1967; 40: 560-4. 3. Barnett AM. Benign recurrent abducens palsy in children. S Afr Med J 1972; 46: 1662-3. 4. Robertson DM, Hines JD, Rucker CW. Acquired sixth nerve paresis in children. Arch Ophthalmol 1970; 83: 574-9. 5. Hunter J. Case history: recurrent sixth nerve paralysis in a child. Aust Orth J 1979-80; 17: 77. 6. Sternherg I, Ronan S, Arnon N. Recurrent, isolated post febrile abducens nerve palsy. J Pediatr Ophthalmol Strah 1980; 17: 323-4. 7. Bixenman WW, von Noorden GK. Benign recurrent VI nerve palsy in childhood. J I'edidtr Ophthalmol Strabis 1981; 18: 29-34. 8. Reinecke RD, Thompson WE. Childhood recurrent idiopathic paralysis ofrhe lateral rectus. Ann Ophthalmol 1981; 13: 1037-9. 9. Werner DB, Savino PJ, Schatz NJ. Benign recurrent sixth nerve palsies in childhood. Secondary to immunisation or viral illness. Arch Ophthalmol 1983; 101: 607-8. 10. Boger Wl', Puliafito CA, Magoon EH er al. Recurrent isolated sixth nerve palsy in children. Ann Ophthalmol 1984; 16: 237-44. 11. Herman JS. Isolated abducens paresis complicating herpes zoster ophthalmicus. Am J Ophthalmol 1962; 54: 298. 12. Nemet P, Ehrlich D, Lazar M . Benign abducens palsy in varicella. Am J Ophthalmol 1974; 78: 859.
Aust NZ J Med 1990; 20
HANKEY
Abstract: The recurrence of an isolated unilateral left abducens nerve palsy on five occasions over five years is described in an adult. No evidence ofany systemic or intracranial disorder has been identified. The aetiology remains uncertain and the clinical course is benign. The diagnosis of 'benign' abducens nerve palsy is one of exclusion and is made retrospectively after an adequate period of serial evaluations. (Aust NZ J Med 1990; 20: 173-174.) Key words: Abducens nerve palsy, recurrent, benign, adult.
The occurrence of horizontal diplopia in association with a unilateral defect of ocular abduction demands a careful neurological examination and search for relevant potential causes of an acquired abducens (sixth cranial) nerve palsy or pseudo-sixth palsy.' Sometimes the diagnosis remains elusive but with time and evolution of the disease process the situation usually becomes clear. I n 1967, Knox et a/., reported 12 children with isolated sixth (VI) nerve palsy in all but one of whom the VI nerve palsy resolved within ten weeks.* They termed this entity 'benign sixth nerve palsy' and speculated that it was due to a preceding viral illness, although a conclusive causal relationship was not demonstrated. In 1972, Barnett reported that benign VI nerve palsy may be recurrent3 (although Robertson et U I . ,inferred ~ this possibility in one of their cases). Since then several case reports have indicated that benign VI nerve palsies in children can be r e c ~ r r e n t . ~ - ' ~ This paper describes, for the first time, the occurrence of benign recurrent unilateral VI nerve palsy in an adult, illustrating that this clinical entity is not confined to children.
CASE REPORT A 41-year-old man presented in December 1987 following the onset of his fifth episode of paralysis of the left lateral rectus muscle. His history dated back to April 1982 when, at age 36, he developed an illness characterised by a slight headache, fever and shivering. Two days later he developed horizontal diplopia due to a left lateral rectus palsy. The left temporalis and masseter muscles were wasted and weak but the remainder of the neurological examination was normal. There was no evidence of myasthenia gravis. Cranial C T scan, with and without contrast, included views of the cavernous sinus and brainstem and was normal. T h e cerebrospinal fluid (CSI;) opening pressure and lahorarory examination was normal. 'The left lateral rectus palsy completely resolved within four months.
In November 1982 he experienced a recurrence of the left lateral rectus palsy which again recovered complerely after two months. In 1984 and 1986 two further episodes of mild horizontal diplopia occurred, each lasting only a few days. In December 1987 he developed an upper respiratory tract infection and five days later noted the acute onset ofhorizontal diplopia in the primary position of gaze, increasing with horizontal gaze to the left. He was otherwise asymptomatic. His past health has been excellent and his family history unremarkable. Abnormalities on examination were confined to the cranial nerves. A left lateral rectus palsy was present, caubing a left esotropia. Wasting and weakness of the left masseter and temporalis muscles were present. 'l'here was no muscle fatigability. Full recovery occurred after two months.
DISCUSSION During the last six years this patient experienced five discrete episodes of paralysis of the left lateral rectus muscle, lasting from several days to four months. Recovery from each episode was spontaneous and complete. On two occasions the episodes were preceded by a non-specific febrile illness. In between attacks, the patient has enjoyed good health. Recurrent unilateral abducens nerve palsy in isolation is an uncommon clinical syndrome which may present diagnostic difficulty. Possible aetiological explanations in the adult include: recurrent infection, either local (otitis media) or systemic (viral);J repeated arteriosclerotic ischaemic microinfarction of the nerve trunk in patients with diabetes mellitus and/or hypertension;' myasthenia gravi$ ophthalrnoplegic migraine; fluctuating intracranial hypertension; a pontine angioma; intermittent nerve compression by a cavernous sinus dural arteriovenous malformation (AVM); a carotid siphon aneurysm in the infraclinoid portion of the cavernous sinus; or a minor anatomical abnormality such as an aberrant anterior inferior cerebellar a ~ t e r y Isolated .~ abducens nerve
Corresporrderrce ro: Dr Graeme J. Hankey, Department of Clinical Neurosciences, Western General Hospital, Crewe Road, Edinburgh, Scotland,
UK EH4 2XU. BENIGN R E C U K R E N r C;NILAI'ERAL AHI)UCEKS NERVE PALSY
Aust K Z J bled 1990; 20
173
palsy could also represent the initial presentation of multiple sclerosis but this diagnosis would be inappropriate before other neurological symptoms and signs of demyelination developed. The long history over more than five years, the complete remissions and the negative clinical features and investigations in this case strongly support the diagnosis of benign recurrent unilateral abducens nerve palsy of uncertain aetiology. The unlikely possibility of an underlying dural AVM or pontine angioma exists but the patient has become Familiar with the spontaneous recovery from each of these episodes and does not wish to proceed further with an MRI examination nor assume the risk of vertebral angiography. The underlying pathophysiology of this entity of benign recurrent abducens nerve palsy is speculative. Abducens nerve palsies can occur in the setting of infection, having been described after herpes zoster ophthalmicus' ' and during the incubation period of varicella.'* A post-infectious (viral) aetiology is certainly suggested by those patients who have developed a VI nerve palsy following immunisatiohs for viral diseases9 and is also implied in those cases, including this patient, in whom palsies developed after systemic illnesses that seemed to be viral in If so, the pathological basis would probably be demyelination or a localised arteritis. Of the five episodes of lateral rectus underaction in this patient, two were preceded by a non-specific febrile illness but two (those in 1984 and 1986) lasted only days. It is difficult to explain the latter episodes in terms of post-viral demyelination or arteritis. Also, several of the recent reports of recurrent isolated VI nerve palsy in children have made a post-infectious aetiology difficult to accept as the most likely factor in all c a s e ~ . ~ ~Reinecke ~.''' and Thompson found no history of concurrent illness in any of the five children they presented and stressed the difficulty in identifying a clear cause for this disorder.s The long-standing left trigeminal motor palsy in this patient is difficult to ignore in this setting. The possibility of a restricted or partial developmental abnormality of the left lower pontine tegmentum, similar to the Mobius syndrome (congenital bi-facial and abducens palsies), exists but its relevance to this entity of recurrent .VI nerve palsy is speculative. The occurrence of a unilateral abducens nerve palsy in a child or adult is important to recognise because it may be the initial manifestation of a progressive intracranial process.
174
If so, it is usually associated with other neurological or systemic abnormalities and if not, such abnormalities usually appear within a few weeks or months. Serial neurological, ophthalmological and radiological (CT or MRI scan) examinations are therefore mandatory. If, with the passage of time, the abducens nerve palsy is the sole neurological abnormality and possible treatable causes have been carefully excluded then it is worthwhile to at least consider the diagnosis of 'benign' abducens nerve palsy so that the patient may be reassured of its favourable prognosis. The value of serial neuro-ophthalmological examinations in these cases is emphasised.
Acknowledgements This patient was under the care of Dr E. G . Stewart-Wynne, Neurologist, Royal Perth Hospital and Dr W. M. Carroll, Neurologist, Sir Charles Gairdner Hospital, Western Australia. Accepted for publication: 9 June 1989.
References I. Glaser JS. Neuro-ophthalmology. Hagerstown, Harper & Row, 1978. 2. Knox DL, Clark DB, Schuster FF. Benign VI nerve palsies in children. Pediatrics 1967; 40: 560-4. 3. Barnett AM. Benign recurrent abducens palsy in children. S Afr Med J 1972; 46: 1662-3. 4. Robertson DM, Hines JD, Rucker CW. Acquired sixth nerve paresis in children. Arch Ophthalmol 1970; 83: 574-9. 5. Hunter J. Case history: recurrent sixth nerve paralysis in a child. Aust Orth J 1979-80; 17: 77. 6. Sternherg I, Ronan S, Arnon N. Recurrent, isolated post febrile abducens nerve palsy. J Pediatr Ophthalmol Strah 1980; 17: 323-4. 7. Bixenman WW, von Noorden GK. Benign recurrent VI nerve palsy in childhood. J I'edidtr Ophthalmol Strabis 1981; 18: 29-34. 8. Reinecke RD, Thompson WE. Childhood recurrent idiopathic paralysis ofrhe lateral rectus. Ann Ophthalmol 1981; 13: 1037-9. 9. Werner DB, Savino PJ, Schatz NJ. Benign recurrent sixth nerve palsies in childhood. Secondary to immunisation or viral illness. Arch Ophthalmol 1983; 101: 607-8. 10. Boger Wl', Puliafito CA, Magoon EH er al. Recurrent isolated sixth nerve palsy in children. Ann Ophthalmol 1984; 16: 237-44. 11. Herman JS. Isolated abducens paresis complicating herpes zoster ophthalmicus. Am J Ophthalmol 1962; 54: 298. 12. Nemet P, Ehrlich D, Lazar M . Benign abducens palsy in varicella. Am J Ophthalmol 1974; 78: 859.
Aust NZ J Med 1990; 20
HANKEY
