Description, Causes and Risk Factors:
Midbrain tegmentum lesion characterized by ipsilateral oculomotor nerve paresis and contralateral paralysis of the extremities, face, and tongue.
It is caused by midbrain infarction as a result of occlusion of the paramedian branches of the posterior cerebral artery or of basilar bifurcation perforating arteries.
Weber syndrome is rare compared to acquired oculomotor nerve palsy. Ischemia is the most common cause of pupil sparing Weber syndrome. Intracranial aneurysms are the most common cause of isolated Weber syndrome involving the pupil.
The majority of Weber syndrome are caused by minor injury to vessels in subarachnoid space or in the cavernous sinus. Less common causes are compression (due to aneurysm or tumor) and inflammation (sarcoidosis and vasculitis). In cases of trauma-related third cranial nerve palsy, underlying lesions such as aneurysms and tumors should be considered and ruled out.
Cerebellar signs (eg, dysmetria, ataxia) are frequent.
Dysarthria and dysphagia typically are present.
As medial rectus is paralyzed and the lateral rectus is unopposed; Diplopia.
Double-vision as one of the eye deviates from the midline.
Inability to move the eye medially or vertically;
If the ipsilateral levator palpebrae superioris is paralysed; Mydriasis.
Unresponsiveness to light as the sphincter pupillae is non-functional and the dilator pupillae is unopposed; Inability for the affected eye to focus on near objects as the ciliary muscles have also been paralysed.
The diagnosis is based on results of a neurologic examination and computed tomography (CT) or magnetic resonance imaging (MRI). If the pupil is affected or if symptoms suggest a serious underlying disorder, CT is done immediately. If a ruptured aneurysm is suspected and CT does not detect blood, a spinal tap (lumbar puncture), magnetic resonance angiography, CT angiography, or cerebral angiography is done.
Treatment if often surgical.
The surgical treatment of third nerve palsies presents a formidable challenge to the ophthalmic surgeon. A complete third nerve paralysis with complete ptosis is best left untreated.
When the paralysis is partial, especially when some adduction is preserved, the patient may benefit from maximal recession of the lateral and resection of the medial rectus muscles. This may be combined with upward transposition of the muscle insertions to counteract the hypotropia. Transfer of the superior oblique muscle to the insertion of the medial rectus muscles with or without fracture of the trochlea has also been recommended.
Ptosis surgery is postponed until alignment of the eyes has been achieved by surgery. Caution with regard to ptosis surgery is advised if elevation is impaired because of exposure problems.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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