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[Persistent isolated abducens nerve palsy from pontine infarction confirmed by gadolinium-DTPA enhanced MRI]
S Hashiguchi1, N Ogasawara, T Igaki
1Department of Neurology, Takamatsu Red Cross Hospital.
Abstract:
An 80-year-old man had left isolated abducens nerve palsy after repeated conjugate deviation to the right without any other findings. MRI demonstrated no abnormal lesion of T2-weighted images, while left paramedian tegmentum pontis was enhanced as responsible lesion by gadolinium (Gd)-DTPA on the 13th hospital day when Foville syndrome lasted. On the 33rd hospital day when isolated abducens nerve palsy lasted, however, this lesion was not detected with Gd enhanced images. The diagnosis of abducens nerve palsy caused by pontine infarction was obtained. Our patient had a lesion involving the left PPRF and ipsilateral abducens nerve. We concluded that the complete damage of left abducens motoneuron may cause isolated abducens nerve palsy lasting more than one year after Foville syndrome due to the dysfunction of left PPRF. To our knowledge, this is the first report of the persistent isolated abducens nerve palsy resulting from a pontine miniature ischemic lesion speculated by Gd enhanced MRI.
Insights
This study reports a rare case of persistent isolated abducens nerve palsy in an elderly man. Pontine infarction affecting the abducens nerve and PPRF caused long-term palsy after Foville syndrome.
Area of Science:
- Neuroscience
- Neurology
- Neuroradiology
Background:
- Abducens nerve palsy can manifest in various forms, including isolated palsies or as part of complex syndromes like Foville syndrome.
- Pontine lesions, particularly ischemic events, are a known cause of cranial nerve dysfunction, affecting motor neurons and their pathways.
Observation:
- An 80-year-old male presented with left isolated abducens nerve palsy following conjugate deviation to the right.
- Initial MRI revealed no T2-weighted abnormalities, but gadolinium-enhanced imaging identified a lesion in the left paramedian tegmentum pontis during Foville syndrome.
- This enhancement resolved by day 33, coinciding with the persistence of isolated abducens nerve palsy.
Findings:
- Diagnosis of pontine infarction affecting the left paramedian pontine reticular formation (PPRF) and ipsilateral abducens nerve was established.
- Complete damage to the left abducens motoneuron is proposed as the cause of persistent isolated abducens nerve palsy.
- The lesion was a miniature ischemic event within the pons, visualized transiently with contrast enhancement.
Implications:
- This case highlights that small pontine ischemic lesions can lead to prolonged isolated abducens nerve palsy, even after resolution of associated symptoms like Foville syndrome.
- It underscores the importance of serial imaging and considering subtle ischemic changes in the pons for diagnosing persistent cranial nerve palsies.
- This is the first reported instance of persistent isolated abducens nerve palsy attributed to a miniature pontine ischemic lesion visualized by enhanced MRI.