The influence of ulnar nerve blockade on skin microvascular blood flow*

Abstract. Microvascular research is seriously hampered by the great temporal and spatial variability of the measured skin blood flow and variation in sympathetic vasomotor reflexes within and between persons. Therefore skin vasomotor reflexes were studied before and after ulnar nerve blockade within the same person, resulting in a temporal complete denervation of the fifth finger and partial denervation of the fourth finger. Skin temperature and laser Doppler flux (LDF) were registrated to measure predominantly arteriove-nous shuntflow. Measurements were performed on the palmar tip of the second and fifth finger in nine healthy volunteers, at baseline, and during a sympathetic reflex test (i.e. inspiratory gasp) and postural response test. Beat-to-beat digital blood pressure was recorded from the third and fourth finger by a Finapres device. Baseline capillary blood cell velocity (CBV) was measured at the nailfold of the second and the fifth finger. After ulnar blockade baseline skin temperature, LDF and CBV increased significantly, with respectively (mean±SE) 3.2±0.9d?C, 20.9 ±5.9 relative perfusion units and 0.79 ±0.40 mm^-1 s. The percentage LDF decrease of the fifth finger during inspiratory gasp was 48.2 ±5.3% before and 31 ±0.9% after blockade. The postural response test showed a decrease in LDF of the fifth finger with no significant difference before and after blockade, respectively 12.3± 14.7% and 8.0±2.7%, while no difference was found in the increase in digital blood pressure in the denervated fourth finger compared to both the same finger before blockade and to the third non-blocked finger. It is concluded that ulnar nerve blockade enables the study of sympathetic skin vasomotor reflexes by comparison of a denervated and a non-denervated vascular bed within the same person. After ulnar blockade arteriovenous shunt flow as well as nutritional capillary blood flow increased significantly. Postural vasoconstrictor response is not abolished by ulnar blockade, suggesting that local regulatory mechanisms are more important.     

Sympathetic vasomotor response of the radial artery in patients with diabetic foot syndrome

OBJECTIVE: Neurophysiological assessment of the peripheral autonomic system is characterized by various limitations. An alternative approach to laser Doppler and venous plethymography is the assessment of the sympathetic vasomotor response of the radial artery obtained by continuous wave Doppler sonography. Nomogram data have been established and demonstrate the temporary disappearance of diastolic flow after coughing or deep inspiration. RESEARCH DESIGN AND METHODS: We assessed the sympathetic vasomotor response in 25 patients (mean age 64 years, range 43-76) with diabetic foot syndrome. The Doppler data were correlated with nerve conduction studies of the median and peroneal nerve, the extent of radiologically diagnosed media sclerosis, and compared with nomogram values (n = 41). RESULTS: Although similar mean flow velocities were found under baseline conditions, the flow pattern was characterized by higher pulsatility in the diabetic group (resistance index [RI] 1.1 vs. 0.7). No significant difference in RI was observed after coughing. The latency of onset of the response was prolonged (2.1 vs. 1.5 s), while the duration of the response did not differ (18 vs. 15 s). Only the nerve conduction velocity of the peroneal nerve correlated inversely with the RI. The extent of radiologically proven calcification tended to correlate with the pulsatility of the baseline signal and the response latencies. CONCLUSIONS: The data obtained by this study suggest the concurrent existence of reduced vessel elasticity due to media sclerosis and dysfunction of the autonomic vasomotor system.     

Detection of autonomic sympathetic dysfunction in diabetic patients. A study using laser Doppler imaging

OBJECTIVE: To study signs of the disturbed reflex autonomic sympathetic nerve function in type 1 and type 2 diabetic patients. RESEARCH DESIGN AND METHODS: Measurements were made on 15 type 1 (duration 13-32 years) and on 50 recently diagnosed type 2 diabetic patients (duration 3-4 years). The vasoconstrictor responses in the distal phalanx of the middle finger (locally heated to 40 degrees C) to the cooling of the contralateral arm were measured using Laser Doppler Imaging (LDI). A vasoconstriction index (VAC) was calculated taking age into account and was compared with reference values obtained in 80 control subjects. The diabetic patients were also studied with deep-breathing tests (i.e., the heart-rate variation expressed as the expiration-to-inspiration [E/I] ratio, a test of parasympathetic nerve function). RESULTS: The vasoconstrictor responses to indirect cooling (VAC) were significantly reduced in the fingers of the diabetic patients, both type 2 (0.77 +/- 0.02 V; P < 0.01) and type 1 (0.83 +/- 0.04 V; P < 0.001), compared with the healthy control subjects (0.65 +/- 0.01); the age-corrected VAC (VACz) was slightly more impaired in type 1 than in type 2 diabetic patients. The frequency of an abnormal VACz corresponded well to the frequency of an abnormal E/I ratio in type 1 diabetic patients (approximately 50%), whereas the frequency of an abnormal VACz was significantly higher than an abnormal E/I ratio among type 2 diabetic patients (11/50 vs. 4/50; P < 0.05). CONCLUSIONS: Both type 1 and type 2 diabetic patients have impaired cutaneous blood flow regulation. The VAC index seems to be a promising tool for detection of subclinical changes in autonomic sympathetic function.     

DC photoplethysmography in the evaluation of sympathetic vasomotor responses

Summary. The d.c. component of the photoplethsmographic signal was used to determine the response of the finger vasculature to three standard tests of vasomotor function: (1) an inspiratory gasp (IG), (2) immersion of the contralateral hand in ice water (IW), and (3) the Valsalva maneouvre. The vasconstrictor response to the first two of these stimuli could be measured in all of 25 normal subjects. The response to the Valsalva maneouvre could not be detected consistently. Seven patients with known sympathetic autonomic dysfunction showed no response to either IG or IW. In 30 patients with diabetes mellitus of over 10 years duration, 46.7% had no response to IG, and 20% had no response to IW. Absent responses correlated with abnormal autonomic cardiovascular reflexes, with absent sympathetic skin responses and with the severity of peripheral somatic neuropathy. The d.c. photoplethysmographic determination of the vasoconstrictor response in the finger after a deep inspiratory gasp and after ice water immersion offers an additional measure of the function of small (2μ-6μ) peripheral nerve fibres. Because of variability in the amplitude of the responses in normals, only an absent response should be accepted as abnormal.     

Neural Circulatory Control in Vasovagal Syncope

The orthostatic volume displacement associated with the upright position necessitates effective neural cardiovascular modulation. Neural control of cardiac chronograpy and inotropy, and vasomotor tone aims at maintaining venous return, thus opposing gravitational pooling of blood in the lower part of the body. The present concept of the vasovagal response or "common faint" implicates the development of inappropriate cardiac slowing due to sudden augmentation of efferent vagal activity, and arteriolar dilatation by sudden reduction or cessation of sympathetic activity. The venous pooling associated with lasting orthostatic stress results in development of central hypovolemia. At a certain point during the ongoing reflex adaptation to the hypovolemia in progress, a depressor reflex is set in train. The depressor reflex input along this second "peripheral" afferent pathway is postulated to originate from various sites in the cardiovascular system but remains uncertain. The common faint in humans is of both vaso- and vagal origin; the pure vagal response is less common than its vasodepressor variant. There is strong evidence for an early loss of vasomotor tone in the majority of fainting subjects. Blocking the vagus nerve or cardiac pacing is not of much help in preventing vasovagal syncope; though atropine or pacing may prevent bradycardia in vasovagal fainting, they have never been proven to prevent hypotension. Baroreflex modulation of autonomic outflow remains present during the presyncopal stages until it becomes offset by an opposing depressor reflex with relative bradycardia and relaxation of arterial resistance vessels. The nature of the vasodilatation associated with the vasovagal response has still not been settled.     

Psychophysiological response patterns of migraine patients in two habituation tests

OBJECTIVE: To investigate the habituation response pattern of patients with migraine to a simple standard stressor and to a more complex performance-dependent (achievement) stressor in three peripheral systems (electrodermal, vasomotor, and cardiovascular). We hypothesized that the migraine patients would show abnormal habituation in these peripheral systems, especially in response to achievement stimuli. BACKGROUND: Abnormal central habituation to repetitive stimuli has been reported frequently in patients with migraine. But little is known about habituation of the peripheral autonomic nervous system to stressors in these patients. METHODS: A total of 30 female migraineurs and 30 physically and mentally healthy women matched for age and social status participated in a simple habituation test (auditory stimuli) and an achievement habituation test (mental arithmetic). RESULTS: Habituation was impaired in the electrodermal (skin conductance response), vasomotor (pulse volume amplitude), and cardiovascular (heart rate response) systems during the mental arithmetic test (achievement stimuli) in the migraineurs as compared to the healthy controls. With the simple stressor (auditory stimuli), however, habituation was impaired in the vasomotor system only. Consistent with these findings were the participants' verbal reports, which indicated significantly more subjective tension in the migraine group than in the control group during the calculation test. CONCLUSION: Our results suggest that the mental arithmetic (achievement) habituation paradigm is an important tool for demonstrating reduced habituation in several specific components of the autonomic nervous system. Further research is needed to target the covariance of central and autonomic nervous system habituation phenomena in migraine.     

Reflex vascular responses in the finger to contralateral thermal stimuli during the normal menstrual cycle: a hormonal basis to Raynaud's phenomenon?

1. Raynaud's phenomenon is a condition which primarily affects women and it must be assumed that hormonal influences are responsible. 2. To further investigate this assumption the effect of cyclic sex hormone fluctuations on the digital vascular reactivity of ten normal young women was studied by the diagnostic techniques of thermal entrainment of finger blood flow and Doppler ultrasound mapping of the digital arteries. 3. In the immediate pre-ovulatory period the results obtained were comparable with those found in patients with established Raynaud's phenomenon, suggesting that oestrogen has an important modulating effect in vivo on reflex peripheral vasomotor responses to thermal stimuli. 4. 'Primary' Raynaud's phenomenon may represent an exaggerated response to oestrogen.     

The relation between sympathetically maintained pain,regional vasomotor disturbances and sympathetic nerve activity: a remaining enigma

In simultaneous bilateral nerve recordings, patients with Sympathetically Maintained Pain (SMP) affecting one limb show similar sympathetic traffic in nerves supplying the affected and unaffected limb, also when the painful limb shows a marked regional autonomic (vasomotor) dysfunction. These findings argue against the notion that SMP must be mediated by a reflex change in the pattern of sympathetic discharge. In general, they underline the fact that autonomic effector disturbances may give little information about underlying nerve traffic.     

Sympathetic vasoconstrictor nerve function in alcoholic neuropathy

Summary. The peripheral sympathetic vasomotor nerve function was investigated in 18 male chronic alcoholics admitted for intellectual impairment or polyneuropathy. By means of the local 133Xenon washout technique, the sympathetic veno-arteriolar axon-reflex was studied. This normally is responsible for a 50% decrease in tissue blood flow, when the ankle is lowered 40 cm below heart level in the supine individual. The patients with moderate to severe polyneuropathy, taken as a group, did not differ significantly from the group of patients with no or only mild polyneuropathy, although a lesser response was seen (18% and 48% decrease respectively). However, in three patients with moderate neuropathy, and in one patient with no signs of neuropathy, this veno-arteriolar reflex was absent, indicating dysfunction' of the peripheral sympathetic adrenergic nerve fibres. The three patients also showed a lesser degree of arteriolar constriction during 45° passive head-up tilt, although none developed symptoms of orthostatic hypotension. Anhidrosis of the feet was found in only three patients. This study lends support to the view that individual differences in the susceptibility to the deleterious effect of alcohol comprise not only the peripheral sensory and motor nerve fibres, but also the thin pseudomotor and vasomotor nerves.     

Biphasic vasomotor reflex responses of the hand skin following intradermal injection of melittin into the forearm skin.

Melittin is the main toxin of honeybee venom. Previously, we have reported that intradermal injection of melittin into the volar aspect of forearm in humans produces a temporary pain and a subsequent sustained increase in the skin temperature due to axon reflex. To clarify the interaction between nociceptive inputs and vascular changes, we studied the influence of noxious stimulation by intradermal melittin on the vasomotor control of the distal extremities in human volunteers. Temperature changes of the bilateral palmar surface were recorded by means of a computer-assisted infrared thermography. Unexpectedly, we found a biphasic response of skin temperature. The skin temperature of both fingers and hands decreased immediately after the melittin injection and then increased well above the control level, prior to the injection. There was a considerable individual variation in the baseline skin temperature, prior to melittin. The skin temperature in a finger/hand with lower preinjection value increased more markedly in the second phase. Consequently, the individual variation in the peak temperature of the second phase was less pronounced. The initial decrease was interpreted as sympathetic vasoconstrictor reflex induced by noxious stimulation and the later increase as release of sympathetic vasomotor tone.     

Myositis ossificans causing ulnar neuropathy: a case report

Myositis ossificans (MO) can compress peripheral nerves and cause neuropathy. We herein describe a patient with ulnar neuropathy caused by MO at the medial elbow. A 28-year-old man with a drowsy mentality and multiple organ damage following a traffic accident was admitted to our hospital. After 3 weeks of postoperative care, the patient’s mental status recovered. However, he complained of severe sharp pain in his left medial forearm and fourth and fifth fingers. He exhibited weak fifth finger abduction and wrist adduction. Severe elbow joint pain was elicited during range-of-motion testing of his left elbow. Ultrasound also showed an edematous, enlarged, hypoechoic ulnar nerve lying above the MO, and the MO outwardly displaced the ulnar nerve. Elbow radiographic examination, computed tomography, and magnetic resonance imaging revealed MO development and compression of the left ulnar nerve. The patient underwent surgery; the following day, his left medial forearm pain completely disappeared with slight improvement in the motor weakness of fifth finger abduction. Ultrasound is a useful tool to easily evaluate the presence of MO and compression of peripheral nerves caused by MO.     

Enhanced pain and autonomic responses to ambiguous visual stimuli in chronic Complex Regional Pain Syndrome (CRPS) type I

Cortical reorganisation of sensory, motor and autonomic systems can lead to dysfunctional central integrative control. This may contribute to signs and symptoms of Complex Regional Pain Syndrome (CRPS), including pain. It has been hypothesised that central neuroplastic changes may cause afferent sensory feedback conflicts and produce pain. We investigated autonomic responses produced by ambiguous visual stimuli (AVS) in CRPS, and their relationship to pain. Thirty CRPS patients with upper limb involvement and 30 age and sex matched healthy controls had sympathetic autonomic function assessed using laser Doppler flowmetry of the finger pulp at baseline and while viewing a control figure or AVS. Compared to controls, there were diminished vasoconstrictor responses and a significant difference in the ratio of response between affected and unaffected limbs (symmetry ratio) to a deep breath and viewing AVS. While viewing visual stimuli, 33.5% of patients had asymmetric vasomotor responses and all healthy controls had a homologous symmetric pattern of response. Nineteen (61%) CRPS patients had enhanced pain within seconds of viewing the AVS. All the asymmetric vasomotor responses were in this group, and were not predictable from baseline autonomic function. Ten patients had accompanying dystonic reactions in their affected limb: 50% were in the asymmetric sub‐group. In conclusion, there is a group of CRPS patients that demonstrate abnormal pain networks interacting with central somatomotor and autonomic integrational pathways.     

Pupil responsiveness in cluster headache: A dynamic TV pupillometric evaluation

In this study the variations in pupil diameter induced by different stimuli (dark-light adaptation, light reflex, electric stimulation of the sural nerve) were investigated in episodic (in the active or remission phases) and in chronic cluster headache (CH) patients. Pupil size monitoring was performed with a monocular, infrared TV pupillometer, and sural nerve stimuli were applied after the pain threshold had been measured as the flexion reflex threshold of the biceps femoris muscle (RIII reflex). The results were compared with those obtained in patients with "peripheral" (third neuron) Horner's syndrome and in healthy sex- and age-matched controls. On the symptomatic side we found an impairment of pupil response to light flashes and nociceptive stimuli; similar findings were sometimes evident on the pain-free side, too. These results substantiate previous observations that in cluster headache a dysfunction of the integrative central nervous system pathways also exists intercritically and mostly bilaterally, involving both autonomic regulation and pain perception mechanisms.     

Sonographic evaluation of primary peripheral nerve repair.

OBJECTIVE. This feasibility study was undertaken to define the potential of sonography for the follow-up evaluation of patients with surgical repair after nerve transection and persistent impairment of nerve function. METHODS. Nineteen patients with primary repair of a transected peripheral nerve because of direct trauma or complex fractures were evaluated with sonography. All patients had persistent clinical symptoms and neurologic signs of impaired nerve function. In 11 patients who underwent second operations, the intraoperative findings were correlated with those of sonography. RESULTS. Reliable identification of repaired nerves with sonography was feasible in all patients. However, in some cases, sufficient visualization of the site of nerve coaptation was problematic because of extensive scarring. Sonographic findings included the appearance of partial discontinuity of nerve fascicles, detection of neuromas, and compression of nerves by overlying scars. Surgical correlation with sonographic findings was excellent for neuroma detection; however, definition of nerve continuity on sonography was sometimes impaired by scarring. CONCLUSIONS: Sonography has a high potential for follow-up examinations of peripheral nerves in relation to previous nerve repair in patients with persistent neurologic signs and symptoms of nerve impairment. Sonography may help in decisions for follow-up surgery by identifying lesions such as neuromas in continuity or discontinuous nerve elements--lesions that will possibly benefit from a second look.     

Spontaneous oscillations in cerebral blood flow velocity give evidence of different autonomic dysfunctions in various types of headache

OBJECTIVES: Our objectives were to determine if: (1) patients with migraine have B wave abnormalities in comparison to normal controls and patients with chronic tension headache and (2) patients with chronic tension headache have an imbalance in autonomic activity that is reflected in differences in Mayer wave activity in comparison to normal controls. BACKGROUND: B waves and Mayer waves are spontaneous oscillations in cerebral blood flow velocity with a frequency of 0.5 to 3 or 4 to 7 cycles per minute, respectively, and can be measured by transcranial Doppler sonography. There is experimental evidence that B waves are generated by certain brain stem nuclei which modulate the lumen of the small intracerebral vessels via monoaminergic nerve endings. In contrast, Mayer waves in cerebral blood flow velocity have no central generator but mirror the Mayer waves in arterial blood pressure which represent peripheral autonomic activity. Migraine may be attributed to a neurotransmitter imbalance in brain stem nuclei. Dysfunctions of the peripheral autonomic nervous system are known in patients with chronic tension headache. METHODS: Using bilateral transcranial Doppler monitoring of the middle cerebral artery B waves and Mayer waves were studied in 30 patients with migraine without aura, 28 subjects with tension-type headache, and 30 normal controls. Coefficient of variation as a quantitative parameter for amplitude of waves and the mean frequency were calculated from the envelope curves of the Doppler spectra. RESULTS: The coefficient of variation of B waves was higher in migrainous patients compared with patients with tension-type headache and normal controls (P<.05), indicating an increase in activity of brain stem nuclei in migraine only. Patients with chronic tension headaches had lower values for Mayer wave activity in comparison with normal controls (P<.05), a sign of an impairment of sympathetic activity. CONCLUSIONS: Our data support the dysfunction of the brain stem monoaminergic/serotonergic system in migraine. In contrast, patients with chronic tension headache have an autonomic dysfunction of peripheral origin presenting as a decrease of sympathetic activity.     

Autoantibodies to autonomic nerves associated with cardiac and peripheral autonomic neuropathy

OBJECTIVE: This study examines whether autonomic nerve autoantibodies (ANabs) are associated with development of autonomic neuropathy using a prospective study design. RESEARCH DESIGN AND METHODS: A group of type 1 diabetic patients were followed prospectively with regard to autonomic nerve function on four occasions. At the third examination, 41 patients were tested for ANabs (complement-fixing autoantibodies to the sympathetic ganglion, vagus nerve, and adrenal medulla), and the results were related to cardiac autonomic nerve function (heart rate variation during deep breathing [expiration/inspiration ratio] and heart-rate reaction to tilt [acceleration and brake index]) and to peripheral sympathetic nerve function (vasoconstriction after indirect cooling [vasoconstriction index]). RESULTS: ANabs were detected in 23 of 41 (56%) patients at the third examination. Compared with patients without ANabs (ANabs-), patients with ANabs (ANabs+) showed significantly higher frequencies of at least one abnormal cardiac autonomic nerve function test at the third examination (17 of 23 [74%] vs. 7 of 18 [39%]; P = 0.03) and fourth examination (15 of 21 [71%] vs. 4 of 16 [25%]; P < 0.01). In contrast, there was no similar difference at the first or second examination. The relative risk for ANabs(+) patients to develop cardiac autonomic neuropathy at follow-up was 7.5 (95% CI 1.72-32.80). The vasoconstriction index was more abnormal in ANabs+ than in ANabs- patients at the fourth examination (median 1.40 [interquartile range 1.58] vs. 0.35 [2.05]; P = 0.01). CONCLUSIONS: ANabs were associated with future development of cardiac and peripheral autonomic neuropathy in diabetic patients, implying an etiological relationship between nervous tissue autoimmunity and these diabetes complications.     

Autonomic cardiovascular responses in old age

Summary. The effect of age on autonomically mediated cardiovascular responses to certain manoeuvres was studied in 15, healthy, old men and women (60–80 years). The results were compared with groups of healthy young (about 25 years) and middle-aged (about 45 years) subjects. There was no significant reduction in cardiovascular responses between the young and middle-aged groups. Respiratory sinus arrhythmia, and heart rate, blood-pressure and contralateral forearm blood flow increases to isometric hand grip, as well as the heart rate decrease during a dive reflex test, were significantly attenuated in the old age group. The Valsalva ratio, and the heart rate and blood-pressure changes during an 8 min orthostatic test did not differ between the old and the two younger age groups. There seems to be only a moderate attenuation of autonomic cardiovascular responses to about 60 years, after which there is a more rapid decline. The difference in reduction between different responses, even those mediated by the same type of autonomic nerve, suggests that the decreased responses are not due to an isolated impaired function of the peripheral autonomic nerve. The impairment may be due to the receptor organ or a combination of defects in function of several parts of the autonomic nervous system in old age.     

糖耐量减低患者神经传导速度及交感皮肤反应的研究

目的:观察糖耐量减低(IGT)患者神经传导速度(NCV)和交感皮肤反应(SSR)的变化。方法:对25例IGT患者(IGT组)、32例2型糖尿病(DM)患者(DM组)及18名对照者(对照组)进行一侧肢体NCV检测和四肢SSR检测。结果:与对照组相比,IGT组(除腓神经外)各根神经NCV均有不同程度减慢,但差异均无统计学意义;DM组(除胫神经外)各根神经NCV与对照组相比差异均减慢(P<0.05)。IGT组双下肢SSR起始潜伏期与对照组相比延长(P<0.05);与对照组相比,DM组四肢SSR起始潜伏期显著延长、波幅显著降低(P<0.01)。对照组、IGT组和DM组NCV异常率分别为5.56%、28.00%、65.63%,SSR异常率分别为33.33%、72.00%、93.75%,3组间NCV和SSR异常率均有显著差异(P<0.01)。在IGT和DM组中,SSR异常率均高于NCV异常率,且无症状者亦有一定的NCV和SSR异常率。结论:IGT患者存在临床或亚临床周围神经损害,以小纤维受累为主,大纤维受累较少且局限于感觉纤维;SSR对糖代谢紊乱相关的周围神经损害的早期诊断敏感性优于NCV,但其特异性较差。     

断指再植术后应用脉搏血氧饱和度仪早期发现血管危象的研究

[目的]早期发现血管危象的发生,提高再植指成活率。[方法]将病人分为A组和B组,A组56例76指,于断指再植术后1d~5d内应用脉搏血氧饱和度仪监测再植指和对侧相应健指的经皮血氧饱和度(SpO2);B组为30例48指断指再植术后发生血管危象的病人,于危象时立即监测再植指和对侧相应健指的SpO2变化。[结果]A组再植指与健指SpO2变化无统计学意义(P>0.05),而B组再植指与健指SpO2差异有统计学意义(P<0.01)。[结论]应用脉搏血氧饱和度仪对再植指进行SpO2监测,能及时发现血管危象,并有助于分析血管危象的类型。     

The Site of Sympathetic Deficit in Cluster Headache

The pattern of autonomic deficit in the face of cluster headache patients resembles the deficit in patients with a postganglionic sympathetic lesion from some other cause; however the presence of abnormal cardiac rhythms and bilateral pupillary reflex deficit in some patients with cluster headache suggests that the lesion might compromise central sympathetic drive. To investigate this possibility, the vasomotor and sudomotor startle reflex was investigated in the hands of sic cluster headache patients with ocular and thermoregulator signs of postganglionic sympathetic deficit in the face; for comparison, responses were also investigated in 15 patients with a lesion in the cervical sympathetic pathway from some other cause. The startle reflex was intact in the hands of the six cluster headache patients, but was diminished ipsilaterally in patients with a central or preganglionic sympathetic lesion and also, surprisingly, in patients with a postganglionic lesion caused by an aneurysm of the internal carotid artery. Ocular sympathetic deficit was greater in patients with an aneurysm of the internal carotid artery than in cluster headache patients or in patients with a postganglionic sympathetic lesion from some other cause; the aneurysm may have compromised neurons with projections to the face and hand, or could have induced transsynaptic degeneration of preganglionic fibers supplying both regions. The findings indicate that central sympathetic drive is not impaired in cluster headache patients; thus, a peripheral lesion probably induces sympathetic deficit on the symptomatic side of the face.