Background: In general, motor neuron disease comprises combined
upper and lower motor neuron diseases, pure lower motor neuron
diseases and pure upper motor neuron diseases. The term lower
motor neuron disease (LMND) may be used for all diseases in which
only lower motor neuron signs are found.

Methods: In this study, we investigated clinical and
electrophysiological features in patients with sporadic LMND. In
order to exclude patients who had amyotrophic lateral sclerosis,
only patients who had had the disease for at least 4 years were
selected. The patients were then classified into three groups based
on the identified pattern of weakness as shown in the registry.

Results: The patients with LMND were categorized into groups of
generalized weakness (group 1, two patients), asymmetrical weakness
of the arms (group 2, 31 patients) and asymmetrical weakness of
the legs (group 3, four patients). Analysis of the results showed
that the distinguished features of group 1 include, an older age at
onset of the disease, more severe weakness and greater functional
impairment. In addition, the results also show that the prognosis of
sporadic LMND seems to be favorable and clinical abnormalities were
confined to one or two limbs in most patients classified by group 2
and 3.

Conclusions: The clinical phenotypes of the different subgroups
described in this study may help to differentiate the several forms
of LMND. Prospective studies are however needed to investigate
whether specific clinical or electrophysiological variables may help
to identify patients with a more benign form of LMND.

KEYWORDS : Amyotrophic lateral sclerosis, Motor neurons, Prognosis, Motor neuron disease