The pseudopolyneuritic form of Amyotrophic Lateral Sclerosis (Patrikios' disease)

The line distinguishing motor neuron diseases (MNDs) from motor neuropathies is sometimes blurred. Among MNDs, the pseudopolyneuritic form of amyotrophic lateral sclerosis (ALS) strictly mimics a neuropathy. We describe the clinical and electrophysiological features in the early stages of the pseudopolyneuritic ALS, and assess the disease progression in eight patients. Early symptoms were unilateral foot-drop and, less commonly, paraparesis. At the clinical examination, weakness of distal and proximal leg muscles was often detected, while the hand muscles were rarely involved and craniobulbar muscles were spared. Definite upper motor neuron signs were rare in the early stages of the disease. Electromyography (EMG) showed active denervation in the lower limbs of all patients (distal > proximal) and in the paraspinal muscles of 7 patients (lumbosacral > thoracic), and more rarely in the upper limbs. Transcranial magnetic stimulation (TMS) yielded abnormal responses (low amplitude or absent cortical motor evoked potentials and prolonged central motor conduction time) in most lower-limb recordings, while mild abnormalities were rarely observed in the upper limbs. Haematologic and cerebrospinal fluid examinations were normal. Brain and spinal MRI showed no significant abnormalities. After a three years follow-up on seven patients, all cases were nonambulatory and had upper limb weakness, and most of them had bulbar dysfunction. The electrophysiological finding of both upper and lower motor neuron involvement of the lower limbs in the early stages of the disease could be a useful marker to distinguish the pseudopolyneuritic form of ALS from other MNDs and motor neuropathies.