On the Site of the Lesion in Konzo : Clinical and Neurophysiological Studies on a Non-Progressive Upper Motor Neuron Disorder

Sammanfattning: Konzo is a permanent spastic para/tetraparesis occurring in undernourished populations in Africa relying on insufficiently processed bitter cassava, which contains cyanogenic compounds, as staple food. Its pathogenetic mechanism is unknown. Our studies aimed at clarifying the lesion in konzo.A preliminary survey on an outbreak of spastic paraparesis in the Democratic Republic of Congo confirmed that it was compatible with konzo. High cyanogenic exposure and low urinary excretion of sulfate were found i.e. mean (±SD) urinary concentration of thiocyanate 1128 (± 670) μmol/L and 4.0 (± 3.30) mmol/L respectively. No antibodies against HIV-1-2 and HTLV- I- II were detected. Patients with konzo (Group I, 21 patients, in 1998; Group II, 15 patients, in 2000) underwent electroencephalography (EEG, 1998), motor evoked potentials (MEPs) using transcranial electrical stimulation (TES, 1998) and transcranial magnetic stimulation (TMS, 2000), and somatosensory evoked potentials (SEPs) with 2- and 4-channel equipment in 1998 and 2000 respectively. Most subjects (12/21) showed generalized slowing of background activity at EEG. TES-MEPs were absent in 9/21 subjects, 10 had prolonged central conduction time (CCT, range 5.9 - 14.9 ms). TMS-MEPs with muscles at rest were absent in 9 and 13 of 14 subjects in arms and legs respectively. Median-SEPs showed absence of scalp responses in 2/21 subjects and 3/15 in 1998 and 2000 respectively. Tibial SEPs showed absence of scalp responses in 15/21 (in 1998) and 7/12 (at left or right side, in 2000). Tibial SEP latencies were prolonged in 6/21 in 1998 (latencies 41.6 - 53.5 ms) and in 6/12 (at any side in 2000, latencies 38.8 - 48.3 ms). Subjects with delayed SEP responses had prolonged CCT (range 23.7 - 29 ms). Most subjects showed normal conduction time to the spinal level i.e. C2 and L1 for median and tibial SEPs respectively.Our findings support involvement of intracranial pathways in konzo. New criteria of konzo are suggested.