A 24-year-old, right-handed man with periodic alternating nystagmus (PAN) due to adrenoleucodistrophy was studied neuro-otologically. In this case, PAN was a comparative large horizontal nystagmus, containing a mild rotatory component, and the amplitude of the nystagmus first increased and then decreased in each span. An average cycle length of the PAN was 180 seconds with a right-beating phase of 95 seconds, a left-beating phase of 75 seconds and null periods of 5 seconds between each phase. The PAN was not affected by eye closure, state of darkness, changing direction of gaze, changing of head position, or the optokinetic nystagmus testing.
However, the PAN continued for about 6 months and then gradually disappeared. CT-scan showed obvious generalized cerebellar and brain stem atrophy.
On comparating this CT-scan with one done 6 months previously, there was a definite increase in cerebellar and brain stem atrophy.
