Infranuclear ocular motor disorders

Congenital isolated unilateral third nerve palsy in children: the diagnostic contribution of high-resolution MR imaging

PURPOSE

To describe the neuroanatomical correlates of unilateral congenital isolated oculomotor palsy by means of high-resolution MRI.

METHODS

Children with a clinical diagnosis of congenital isolated oculomotr palsy and with a high-resolution MRI acquisition targeted on the orbits and cranial nerves were selected and included in the study. An experienced pediatric neuroradiologist evaluated all the exams, assessing the integrity and morphology of extraocular muscles, oculomotor, trochlear and abducens nerves as well as optic nerves and globes. Clinical data and ophthalmologic evaluations were also collected.

RESULTS

Six children (age range: 1-16 years; males: 3) were selected. All patients showed, on the affected side (left:right = 5:1), anomalies of the III nerve and extraocular muscles innervated by the pathological nerve. One patient had complete nerve agenesis, two patients showed a diffuse thinning of the nerve, from the brainstem to the orbit and 3 patients showed a distal thinning of the oculomotor nerve, starting at the level of the cavernous sinus. In all cases atrophy of corresponding muscles was noticed, but the involvement of the affected muscles varied with the nervous pattern of injury.

CONCLUSIONS

High-resolution MRI represents a valuable tool for the diagnosis of III nerve anomalies in unilateral congenital IOP, showing different patterns of nerve involvement and muscular atrophy.

Ocular neuromyotonia

Ocular neuromyotonia is a rare, albeit treatable, ocular motor disorder, characterised by recurrent brief episodes of diplopia due to tonic extraocular muscle contraction. Ephaptic transmission in a chronically damaged ocular motor nerve is the possible underlying mechanism. It usually improves with carbamazepine. A 53-year-old woman presented with a 4-month history of recurrent episodes of binocular vertical diplopia (up to 40/day), either spontaneously or after sustained downward gaze. Between episodes she had a mild left fourth nerve palsy. Sustained downward gaze consistently triggered downward left eye tonic deviation, lasting around 1 min. MR scan of the brain was normal. She improved on starting carbamazepine but developed a rash that necessitated stopping the drug. Switching to lacosamide controlled her symptoms.

Recurrent Isolated Oculomotor Nerve Palsy after Radiation of a Mesencephalic Metastasis. Case Report and Mini Review

Introduction: Recurrent oculomotor nerve palsies are extremely rare clinical conditions.

Case report: Here, we report on a unique case of a short-lasting recurrent unilateral incomplete external and complete internal oculomotor nerve palsy. The episodic palsies were probably caused by an ipsilateral mesencephalic metastasis of a breast carcinoma and occurred after successful brain radiation therapy.

Discussion: While the pathogenic mechanism remains unclear, the recurrent sudden onset and disappearance of the palsies and their decreasing frequency after antiepileptic treatment suggest the occurrence of epilepsy-like brainstem seizures. A review of case reports of spontaneous reversible oculomotor nerve palsies is presented.