Skin Vasomotor Reflex in a Patient with Brainstem Dysfunction Shin-ichi Tsunoda, MD, Kazumasa Shindo, MD, and Zenji Shiozawa, MD

Temporary reduction of fingertip or toe blood flow follow- ing pain stimulation, deep inspiration, cold exposure, tone stimulation, or mental stress is known as the skin vasomotor reflex (SVMR),’,2 but its neural pathway is not fully under- stood. We investigated SVMR in a 74-year-old man with severe brainstem dysfunction.

On admission, the patient was in a deep coma with apnea and quadraparesis and was mechanically ventilated. The pu- pils were dilated, and light reaction and the oculocephalic reflex were absent. Computed tomography revealed a massive cerebellar hematoma severely compressing the brainstem. Brainstem auditory evoked potentials and caloric testing showed no response. Painful stimuli to the toes elicited spi-

nal automatism (nociceptive spinal flexion reflex) in the lower extremities. Spinal automatism was observed until the fourth hospital day but was no longer seen from the fifth hospital day to the seventh, when the patient died. SVMR was measured using a laser Doppler blood flowmeter at the right great toe after application of painful stimuli to the toe (pinching) and after forced deep inspiration using the respi- rator (intrabronchial pressure up to 40 mm Hg) (Fig). SVMR was evoked normally until the fourth hospital day, but on the sixth hospital day, the day after spinal automa- tism disappeared, SVMR also disappeared.

Three reflex pathways have been demonstrated-spinal, medullary, and suprapontine-as the source of SVMR evoked by somatic nerve stimulation (electric stimuli) in animal^.^ In humans, Magerl and colleagues4 found that SVMR to nociceptive stimulation is mainly processed at the spinal level. Kano and associate^,^ who conducted experi- ments in which they used peripheral nerve blockade or spinal

Paink1 stimuli

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Fig. (A) Skin vasomotor reflex to pain and deep inspiration in a normal 65-year-old man. The skin blood flow of the great toe normally decreased following pain stimuli and deep inspiration. (23) Skin uasomotor reflex to pain and deep inspiration of the patient with brainstem dysjbnction on the fourth hospital day when the spinal autorna- tism was present. A normal skin uasomotor reflex o f toe was observed. (C) Skin vasorno- tor reflex to pain and deep inspiration o f the patient with brainstem dys&nction on the sixth hospital day, The skin vasomotor reflex disappeared simultaneously with the spinal automatism. The vertical bar indi- cates the calibration of skin blood flow in ml/min/lOO g tissue volume. The arrows indicate the initial point o f stimulation.

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anesthesia at various levels, speculated that the reflex arc of SVMR induced by deep inspiration may be present in the thoracic spinal cord.

In our patient, neurological findings met the criteria for brainstem death, but the presence of spinal automatism in- dicated that the spinal cord was at least partially preserved. The patient's SVMR was elicited on the fourth hospital day, even though there was severe brainstem damage. However, SVMR and spinal automatism disappeared on the sixth hos- pital day. These observations indicate that SVMR disappears when the damage reaches the spinal cord and suggest that the reflex arc of SVMR may be present in the spinal cord in addition to the supraspinal pathway.

Department o f Neurdogy, Yamanashi Medical CoLege, Yamanashi, Japan

References 1. Low PA, Neumann C, Dyck PJ, et al. Evaluation of skin vaso-

motor reflexes by using laser Doppler velocimetry. Mayo Clin Proc 1983;58:583-592

2. Kana T, Shimoda 0, Higashi K, et al. Fundamental patterns and characteristics of the laser-Doppler skin blood flow waves recorded from the finger or roe. J Auton New Sysr 1393;45:

3. Sat0 A. Somata-sympathetic reflex discharges evoked through su- pramedullary pathways. Eur J Physiol 1972;332:117-126

4. Magerl W, Geldner G, Handwerker H O . Pain and vascular reflexes in nian elicited by prolonged noxious mechano- stimulation. Pain 1990;43:219-225

5. Kana T, Shimoda 0, Higashi K, Sadanaga M. Effects of neural blockade and general anesthesia on the laser-Doppler skin blood flow waves recorded from the finger or roe. J Auron Nerv Sysr 1994;48:257-266

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