The features or mechanisms of dyshidrosis have not been sufficiently clarified. Neither has the difference between hyperhidrosis and hypohidrosis. To clarify the features and mechanisms of dyshidrosis (hyperhidrosis and hypohidrosis) in syringomyelia, the clinical features focusing on hidrosis of 30 patients with syringomyelia and Chiari malformation located from a syringomyelia database were prospectively analysed. The patients were classified into three groups: eight patients (26.7%) had segmental hypohidrosis, 10 (33.3%) had segmental hyperhidrosis, and 12 (40.0%) had normohidrosis. We found that the Karnofsky functional status for the hyperhydrosis and normohidrosis groups were significantly higher than for the hypohidrosis group (p=0.0012), with no significant differences between the hyperhidrosis and normohidrosis groups. The duration from the onset of syringomyelia to the current dyshidrosis was significantly longer in the hypohidrosis group than in the hyperhidrosis group (p=0.0027). A significant correlation was identified between the duration from the onset of syringomyelia to the time at study and the performance score (r=−0.599, p=0.0003). The results substantiate previous hypotheses that in its early stage syringomyelia causes segmental hyperactivity of the sympathetic preganglionic neurons, and hyperactivity of these gradually subsides as tissue damage progresses. Focal hyperhidrosis may be regarded as a hallmark of a relatively intact spinal cord, as well as normohidrosis.
- Chiari malformation
- sympathetic preganglionic neuron
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Syringomyelia is responsible for dyshidrosis as well as other disorders of the autonomic nervous system.1-4 Although the link between syringomyelia and focal dyshidrosis (hyperhidrosis and hypohidrosis) has been described, no adequate notice has been taken of the phenomenon,1 5-8 nor has its mechanism been properly explained.1-3 9-11 Furthermore, no descriptions have been offered of any relation between hyperhidrosis and hypohidrosis.
PATIENTS AND METHODS
We have stored clinical data of a consecutive 34 patients (0.28%) with MRI confirmed syringomyelia and Chiari malformation among the 11 967 outpatients who visited our neurology clinic from April 1989 to November 1996. Three quarters of the patients came without referral, and a quarter came with referral. Our outpatient clinic is not only a primary but also a secondary and tertiary centre for diagnosis and treatment of all neurological disorders. The case records of each patient showed that there had been no referral bias to our clinic as a consequence of our interest in dyshidrosis in syringomyelia. The protocol includes items for the autonomic nervous system as well as other systems. The data were obtained prospectively, with the intention of avoiding any predetermination bias, according to a protocol for examining patients with syringomyelia, which we ourselves designed. At the time of registration for this study, we obtained informed consent from patients to enter their information into our study database. Four of the 34 patients were dropped from the study because they refused to give us permission to employ clinical information about themselves for any clinical study; this left 30 patients. Twelve of these patients were operated on for syringomyelia, and we completed entering their information at the time of the operation.
PROTOCOL FOR EXAMINING DYSHIDROSIS
We obtained detailed clinical information for each patient, including their previous experience of hidrosis. A structured protocol was used to examine the state of hidrosis: step 1 asking about the nature and distribution of the hidrosis and the effects of room temperature, exercise, clothing, psychological burdens, food, etc; step 2 examining the state of hidrosis by observation, manual examination, and drawing a metal spoon across the surface of the skin (spoon test12) either after adequate physical exercise or when lying in a bed warmed in advance by electric blankets. When further investigation was necessary to clarify the nature and distribution of dyshidrosis, the following steps were performed; step 3 taking a thermograph in a room at a temperature of 21–28°C; step 4 a hidrosis examination (the iodine-starch method) at a room temperature of 45–50°C, or in a bed warmed in advance. Consequently we performed thermography in 16 patients, and the iodine-starch method in nine patients. We assessed the performance status by Karnofsky performance score (K score); this ranges from 0 to 100, and the higher the score, the better the performance.13
(See also our previous case records for three patients with hyperhidrosis14).
Patient 18 (hyperhidrosis; 37 year old woman) had a 7 month history of persistent hyperhidrosis and pain in the left upper quadrant of the body. There was no muscle weakness or atrophy. Thermography showed low temperature in the left upper quadrant, which was consistent with hyperhidrosis of the area (figure A). She underwent an operation (a syringosubarachnoid shunt) 7 months after onset, after which hyperhidrosis and pain subsided within a week, as indicated by thermography (figure B).
We performed a statistical analysis of five factors (age at time of study, age of onset of symptoms, duration from onset of symptoms to time of study, K score, and duration of follow up period) for the three groups of patients (hyperhidrosis, normohidrosis, and hypohidrosis) by one way factorial analysis of variance (ANOVA) (Fisher’s PLSD method as a post hoc test), and for two factors (age of onset of current dyshidrosis and duration from onset of symptoms to current dyshidrosis) between the two groups of patients (hyperhidrosis and hypohidrosis) by non-paired t test. We then obtained the Pearson’s correlation coefficient for duration from onset of symptoms to time of study, and K score for all 30 patients.
Of the 30 patients, eight (26.7%) had hypohidrosis, 10 (33.3%) had segmental hyperhidrosis, and 12 (40%) had normohidrosis. In all patients, the distribution of dyshidrosis corresponded with the location of the syrinx and other neurological manifestations; the syrinx was located roughly in the region from the central canal to the unilateral (or sometimes bilateral with asymmetry) posterior angle of the spinal cord.
We have summarised the results of the statistical analyses in the table. Although we ourselves were not able to confirm any change in the features of hidrosis during the follow up period, the clinical histories of five patients indicate that hidrosis decreased segmentally or diffusely over a long period. Duration from onset of symptoms to study was significantly longer in the hypohidrosis group than the normohidrosis group (ANOVA; F(2, 27)=4.127, p=0.0273) (table). The K scores were significantly higher in the hyperhidrosis and normohidrosis groups than in the hypohidrosis group (ANOVA; F(2, 27)=8.765, p=0.0012), with no significant difference between the hyperhidrosis and normohidrosis groups (p=0.7282). Duration from onset of symptoms to current dyshidrosis was significantly longer in the hypohidrosis than in the hyperhidrosis group (p=0.0027). There were no significant differences between hidrosis groups in the other factors. A significant correlation between the two items (duration from onset of symptoms to study, and K score) was recognised (r=−0.599, n=30, p=0.0003).
We performed a MEDLINE search for publications dealing with dyshidrosis in syringomyelia between January 1966 and June 1997, with a language limitation of English, German, and French. This search confirmed the scant accumulation of information regarding dyshidrosis in syringomyelia; we were able to locate only four cases accompanied by Chiari malformation (three of which we have already reported and are currently included in this study).10 14
We previously speculated that hyperhidrosis is caused by stimulation of sympathetic preganglionic neurons (SPGNs) rather than interference to the inhibitory tract.14 This is equivalent to the hypothesis regarding body hypertrophy which we recently presented.4 Later, disinhibition of the inhibitory local interneurons (ILINs), which are located in the vicinity of SPGNs, was supposed to be the cause of segmental hyperactivity of the SPGNs.10 When, in the clinical course of syringomyelia, slowly progressive tissue damage around the syrinx3reaches the lateral horn, it will segmentally affect the SPGNs or adjacent structures.14 This time our results have shown, from the viewpoint of sweating, that there evidently is a hyperactivity of the SPGNs as long as the disability is mild; however, as the disability progresses, the hyperactivity gradually decreases and is replaced by hypoactivity (table).
We have a choice of two possibilities for the mechanism responsible for the hyperactivity of the SPGNs so far; the first is that the SPGNs are stimulated directly by a minimal tissue damage; the second is damage to the ILINs10 (preceding the damage to the SPGNs)—we have recently acquired some knowledge of these ILINs.15 16 In either case, as the disease progresses, hyperactivity will shift to normoactivity and finally to hypoactivity because of progressive and irreversible damage to the SPGNs, consistent with the clinical history of five of our eight patients with hypohidrosis. By contrast, immediate resolution of hyperhidrosis after decompression of the syrinx in patient 18, whose disability was minimal, showed that the damage to the SPGNs was mild and tends to be reversible in patients with mild disability (figure). Before we reached the above hypothesis for the mechanism of hyperhidrosis, we had ruled out the possibility of interference to the inhibitory tract that connects the upper centre and the SPGNs as before because of the segmental distribution of hyperhidrosis and because of the locational relation among the syrinx, inhibitory tracts, and SPGNs.14 16
Current results substantiate previous speculation about the mechanism of and relation between hyperhidrosis and hypohidrosis in syringomyelia.3 9 14 We now think that, in syringomyelia, focal hyperhidrosis can be regarded as a hallmark of a relatively intact—even though slightly damaged—spinal cord. We also think that, in syringomyelia, some part of normohidrosis is associated with a considerable amount of spinal cord damage. We propose that in diagnosing focal dyshidrosis, more attention should be given to the possibility of syringomyelia.
We are indebted to Drs Kazutoshi Hida, Yoshinobu Iwasaki, and Hiroshi Abe (Department of Neurosurgery, Hokkaido University School of Medicine) for their help in providing us with clinical information regarding surgical treatment. This study was supported by Research Grant (5B-3) for Nervous and Mental Disorders, from the Japanese Ministry of Health and Welfare.