Introduction: In spite of the rarity of isolated paralysis of the third cranial nerves in infancy, we present an acquired cryptogenic case which had an excellent, rapid response to treatment with corticosteroids started three months after onset of the condition.
Clinical case: A girl aged three and a half years, with no significant past clinical history, presented with a third cranial nerve syndrome of sudden onset, with divergent squint and right ptosis, but no changes in pupil reactivity. All the complementary tests done were normal. After three months of observation, since the condition persisted, treatment was started with oral prednisone 2 mg/kg/day for three months. The ptosis disappeared in two weeks, and two years after treatment was stopped has not reappeared. The absence of pain would suggest that this was not a Tolosa-Hunt syndrome, although pain-free episodes have been described. The absence of alteration in pupil reactions is against, although does not exclude, compression of the third cranial nerve. This finding, together with the spectacular response to corticosteroids would support the diagnosis of inflammation limited to the motor fibres, probably due to a viral infection.
Conclusion: We conclude that corticosteroids may be considered in the treatment of cryptogenic cranial neuropathy, once other possible aetiologies have been excluded, with the object of modulation of the theoretical immune mechanisms involved.