We delineated the clinical and laboratory features that help distingui
sh acute myelopathic MS (MMS) from acute transverse myelitis (ATM), sp
ecifically testing the hypothesis that the symmetry of motor and senso
ry impairments at presentation can reliably distinguish between ATM an
d MMS. We reviewed 20 consecutive patients with ATM and 16 patients wi
th MMS. Clinical criteria were used to assign patients to the ATM grou
p. Patients assigned to the MMS group had onset of MS symptoms referab
le to the spinal cord and eventually fulfilled Poser's criteria for MS
. The relative contribution of the symmetry of both motor and sensory
symptoms for the accurate identification of ATM versus MMS was evaluat
ed using a discriminant function analysis. Fifteen of 16 MMS patients
and all 20 ATM patients presented with symptoms of motor dysfunction.
Additionally, all patients in both groups presented with sensory compl
aints. MMS patients had asymmetric motor or sensory symptoms in all bu
t one patient, whereas ATM patients exhibited symmetric weakness unifo
rmly and symmetric sensory loss in all but one patient (statistically
significant). None of the MS patients met criteria for ATM at presenta
tion. None of the ATM patients developed MS over an average follow-up
period of 4.5 years. In conclusion, MMS was easily distinguished from
ATM in this study.