Atypical motor neuron disease with severe ophthalmoloplegia: a report of two cases

Transition from the locked in to the completely locked-in state: a physiological analysis

OBJECTIVE

To clarify the physiological and behavioral boundaries between locked-in (LIS) and the completely locked-in state (CLIS) (no voluntary eye movements, no communication possible) through electrophysiological data and to secure brain-computer-interface (BCI) communication.

METHODS

Electromyography from facial muscles, external anal sphincter (EAS), electrooculography and electrocorticographic data during different psychophysiological tests were acquired to define electrophysiological differences in an amyotrophic lateral sclerosis (ALS) patient with an intracranially implanted grid of 112 electrodes for nine months while the patient passed from the LIS to the CLIS.

RESULTS

At the very end of the LIS there was no facial muscle activity, nor external anal sphincter but eye control. Eye movements were slow and lasted for short periods only. During CLIS event related brain potentials (ERP) to passive limb movements and auditory stimuli were recorded, vibrotactile stimulation of different body parts resulted in no ERP response.

CONCLUSIONS

The results presented contradict the commonly accepted assumption that the EAS is the last remaining muscle under voluntary control and demonstrate complete loss of eye movements in CLIS. The eye muscle was shown to be the last muscle group under voluntary control. The findings suggest ALS as a multisystem disorder, even affecting afferent sensory pathways.

SIGNIFICANCE

Auditory and proprioceptive brain-computer-interface (BCI) systems are the only remaining communication channels in CLIS.

Atypical motor neuron disease with supranuclear vertical gaze palsy and slow saccades

In amyotrophic lateral sclerosis (ALS), eye movements are usually preserved even after the long-term use of respirators. The present study evaluated a 57-year-old male patient who showed clinical findings compatible with ALS but exhibited disorders of eye movements before he needed to be on an artificial respiration system. The patient had noted clumsiness and weakness in all extremities 5 years before presentation of abnormal eye movements. The results of electromyography and muscle biopsy were compatible with ALS. However, supranuclear vertical gaze palsy and slow saccades are seen. The present case might be representative of a distinct clinical entity, motor neuron disease with disorders of eye movement.