Periodic Alternating Nystagmus in Phenytoin Intoxication

Periodic alternating nystagmus and rebound nystagmus in spinocerebellar ataxia type 6

“…PAN has been reported to be associated with congenital and with several acquired cerebellar disorders,7–12 and it is assumed to represent an instability or increased gain in the vestibulo‐ocular reflex 8, 10. PAN also can be induced by certain drugs, e.g., phenytoin,13 phenobarbital14 or primidone,14 but the drugs that Patient 1 had taken have not been reported to induce PAN. Animal experiments have revealed that the cerebellar nodulus and uvula are important in habituating and stabilizing the vestibule‐ocular reflex, and selective ablation of these areas produces PAN,15 suggesting that the uvula and nodulus are responsible for PAN.…”

Abnormal Eye Movements in Children

“…41 One case has been observed with therapeutic levels of lithium 43 and another from phenytoin toxicity. 44 Acquired PAN is thought to result from disruption of the nodula and uvula of the cerebellum, which in turn reduces tonic 45 PAN may occur together with CN, but may be difficult to recognize because of the relatively long cycle time for the shift in the direction of nystagmus. Patients with both PAN and CN usually have abnormal head postures that shift at the same time as the shift in the direction of the nystagmus.…”

Ocular complications of neurological therapy

“…, 1978), but only rarely downbeat nystagmus (Berger and Kovacs, 1982; Chrousos et al. , 1987), periodic alternating nystagmus (Campbell, 1980), and partial or total gaze palsy (Mullaly, 1982; Fredericks et al. , 1986).…”

“…Eye movements may be affected by therapeutic or toxic doses of antiepileptic drugs, or by idiosyncratic reactions. Phenytoin, carbamazepine and phenorbarbitone commonly cause diplopia and gaze-evoked nystagmus (Rashbass, 1959;Umeda and Sakata, 1977;Riker et al, 1978), but only rarely downbeat nystagmus (Berger and Kovacs, 1982;Chrousos et al, 1987), periodic alternating nystagmus (Campbell, 1980), and partial or total gaze palsy (Mullaly, 1982;Fredericks et al, 1986). The likelihood of adverse effects on eye movements increases with antiepileptic polytherapy.…”