Visually Evoked Sympathetic Skin Response in Normal Subjects

BACKGROUND: Sympathetic skin response (SSR) is a transient change in the electrical potential of the skin that is evoked by internal or external stimuli. In the present study, our purpose was to compare electrical and visual stimulation methods of evoking a SSR. METHODS: SSRs evoked by both electrical and visual stimulation were recorded from the palm and sole from 48 healthy volunteers. RESULTS: SSRs were obtained in all normal control subjects following both electrical and visual stimulation. The latency of SSR following electrical stimulation was 1383.75+/-223.56 msec at the palm and 1790.54+/-318.70 msec at the sole, and that following visual stimulation was 1518.75+/-252.64 msec at the palm and 1930.10+/-226.19 msec at the sole. The latencies of SSRs following visual stimulation were prolonged significantly more than those following electrical stimulation. The amplitudes of SSRs following visual stimulation were significantly lower than those following electrical stimulation, and the amplitude of SSRs following both electrical and visual stimulation had marked intersubject and intrasubject variabilities in each of the stimulations. CONCLUSIONS: The SSR evoked by visual stimulation is as reliable as known electrical stimulation for determining sympathetic functions and is a less invasive method. Latencies by visual stimulation are longer than those by electrical stimulation in both the palm and sole. The visual stimulation method of evoking a SSR is not influenced by an ascending somatosensory pathway theoretically, so we can postulate that it reflects a purely autonomic function if there is no problem in the visual pathway.

Episodic Central Neurogenic Hyperventilation in an Awake Patient with Unilateral Pontine Infarction

Central neurogenic hyperventilation (CNH) is characterized by sustained tachypnea inspite of an elevated arterial PaO2, pH and a low arterial PaCO2. CNH is common in patients with brainstem injury accompanied by a decreased level of consciousness but this also has been described in some alert patients with an invasive brainstem tumor. We report one case with CNH resulting from a unilateral pontine infarction. His consciousness was clear, and CNH spontaneously disappeared without any medication.

A Case of Idiopathic Ocular Neuromyotonia

Ocular neuromyotonia (ONM) is an episodic involuntary contraction of one or more extraocular muscles, resulting from spontaneous neural discharges of ocular motor nerves. Previous radiation therapy to pituitary or other juxtasellar tumor and vascular compressions are the most common reported causes of ONM. We report one unique case of ONM involving the abducens nerve without any other organic brain lesion and prior radiation therapy.

Two Cases of Spinal Cord Infarction: Vertebral Stenosis and Systemic Hypoperfusion

We experienced two cases of cord infarction. One patient developed quadriparesis and impaired pain and temperature sensation, whose T2-weighted MRI revealed a high-intensity lesion from medulla to C5. Angiography showed severe stenosis of both vertebral arteries. Another patient developed paraplegia and loss of all sensory modalities after cardiac arrest, whose T2-weighted MRI revealed a high-intensity lesion in the cord at T11-L1. We conclude that each cause of the infarctions was stenosis of the vertebral arteries and systemic hypoperfusion.