Masafumi Machida

An Experimental Study in Chickens for the Pathogenesis of Idiopathic Scoliosis

Experimentaliy induced scoliosis was investigated in pinealectomized chickens using pathologic and neurophysiologic means. A total of 90 chickens were tested; 30 served as a normal control 30 received an autografted pineal body in the intramuscular tissue of the trunk, and 30 underwent pinealectomy without autograft. Scoliosis developed in all pineslectomized chickens within 2 weeks, showing gradual progression during the next 5 or 6 weeks. At 3 months, the three-dimensional spinal deformity consisted of lateral curvature and vertebral body rotation, resulting in a praminent lordoscoliosis at the thoracic level. In contrast, scoliosis developed in only 10% of the autagrafted chickens. Histologic examination revealed no pathologic change in the brain in either the pinealectomized scoliosis group or in the autografted nonscoliosis group. Cortical potentials in the scoliosis group were delayed, thus suggesting conduction disturbance rostral to the brain stem. Although the relationship between the cause and effect is uncertain, these findings implicate neurotransmitters or neurohormonal systems in the pineal body as a major contributing factor in this type of axperimental scoliosis.

Melatonin. A possible role in pathogenesis of adolescent idiopathic scoliosis.

Study Design. The serum melatonin levels during 24‐hour periods were compared between patients with idiopathic and age‐matched normal control subjects. Objective. To find if the melatonin deficiency may have some role for progression or etiology of idiopathic scoliosis in humans. Summary of Background Data. Experimentally induced scoliosis in chicken by pinealectomy can be attributed to the defect in melatonin metabolism. Method. Blood samples were correlated every 3 hours during 24‐hour periods, and serum melatonin levels were measured and statistically analyzed. Results. The level of melatonin, integrated concentration through 24 hours and night time (0:00 AM‐6:00 AM), in the patients who had progressive curve (more than 10° of progression in the previous 12 months) was significantly lower than the level in the patients who had a stable curve (less than 10° of progression in the previous 12 months) or in the control subjects (P<0.05). Conclusion. The study suggests that normal melatonin synthesis or metabolism may have crucial role in regulating normal spine growth. The level of melatonin appears to be a useful predictor for progression of spine curvature in idiopathic scoliosis.

Cause of idiopathic scoliosis.

Idiopathic scoliosis is a three-dimensional deformity of the spine with lateral curvature combined with vertebral rotation. The primary lesion, however, lies in the median sagittal plane, taking the form of a lordosis. It was first described by Hippocrates, and the term “scoliosis” was first used by Galen (AD 131–201). Although the clinical manifestations of scoliosis have been well described, no one has been able to determine the cause and pathogenesis. Throughout the 18th and 19th centuries, scoliosis was believed to be caused by postural positioning of the body. Historically, idiopathic scoliosis has been attributed to a wide variety of conditions ranging from poor posture to poor nutrition. Nutritional deficiency was proposed as a cause in the beginning of this century, and most spinal curves were thought to be secondary to rickets. Brunk, however, showed that the curves identified as rickets presumably caused by vitamin D deficiency never became severe and actually were reversible by treatment. Recently, the search for the cause of idiopathic scoliosis has focused on the structural elements of the spine, spinal musculature, collagenous structures, endocrine system, central nervous system, and genetics. Of all these studies, none has shown convincing evidence of the cause of idiopathic scoliosis. Results of experiments on various animal models and clinical studies have indicated possible anatomic or functional influences in the cause of idiopathic scoliosis, but many of them may be epiphenomena rather than causes. More recently, Kindsfater et al have reported that the level of platelet calmodulin in skeletally immature patients with a progressive spine curve is significantly higher than in those with a stable curve. Machida et al found significantly decreased nighttime melatonin levels in adolescents with progressive curves, whereas those with stable curves had a level that is normal for adolescents There is a strong interaction of melatonin with calmodulin. Other researchers have suggested a genetic component in idiopathic scoliosis because of the similarity of curve pattern in twins who both have scoliosis. This is a review of various causative factors thus far proposed for idiopathic scoliosis and a discussion of where research is heading to determine the cause of idiopathic scoliosis.

Pathogenesis of idiopathic scoliosis. Experimental study in rats.

STUDY DESIGN A radiographic examination of pinealectomized rats to observe the development of scoliosis and halt the condition by administration of melatonin. OBJECTIVES To discover whether pinealectomy has the same effect in mammals as shown in the chicken, and to determine whether the bipedal condition is important for development of scoliosis. SUMMARY OF BACKGROUND DATA Pinealectomizing chickens shortly after hatching consistently resulted in scoliosis closely resembling human idiopathic scoliosis. It has not been determined whether this phenomenon is restricted solely to chickens, or if this experimental model is applicable to other animals, especially those more closely related to humans. METHODS A sham operation in five bipedal rats served as the control in this study. Pinealectomy was performed in 10 quadrupedal rats, pinealectomy in 20 bipedal rats, and pinealectomy with implantation of melatonin pellet in 10 bipedal rats. Spinal radiographs were used to measure the degree of scoliosis at 3 months after surgery. RESULTS Scoliosis developed only in pinealectomized bipedal rats and not in quadrupedal rats. It developed in none of the sham operation group and in only 1 of 10 pinealectomized bipedal rats with melatonin treatment. CONCLUSIONS Melatonin deficiency secondary to pinealectomy alone does not produce scoliosis if the quadrupedal condition is maintained. The bipedal condition, such as that in chickens or humans, plays an important role in the development of scoliosis. The findings suggest a critical influence of a postural mechanism for the development of scoliosis.

Far‐field somatosensory evoked potentials after stimulation of the tibial nerve

In 21 normal subjects, far-field somatosensory potentials were recorded from the scalp after stimulation of the tibial nerve at the ankle (tibial SEP). With the use of a knee reference contralateral to the side of stimulation, the tibial SEP consisted of three major positive peaks, P17, P24, and P31, and three additional but inconsistent components, P11, P21, and P27. Presumable generator sources of the tibial SEP are the popliteal fossa for P11, entry to the sacral plexus for P17, the cauda equina for P21, entry to the conus medullaris for P24, the rostral spinal cord for P27, and the brainstem for P31.

Pathogenesis of idiopathic scoliosis: SEPs in chicken with experimentally induced scoliosis and in patients with idiopathic scoliosis.

We studied somatosensory evoked potentials (SEPs) in 20 chickens with experimentally induced scoliosis after pinealectomy and in 100 patients with idiopathic scoliosis. We also studied 20 chickens without scoliosis and 20 healthy youngsters. In the chickens, SEPs after leg stimulation was significantly delayed in the scoliosis group compared to the controls. In patients, the latency of cortical potential (N37) after stimulation of tibial nerve was longer in the scoliosis group than in the controls. Our findings in both experimental and clinical studies strongly support the hypothesis that idiopathic scoliosis results from dysfunction in the central nervous system. The type of SEPs abnormalities described in idiopathic scoliosis suggest a pathology from the midbrain to the cortex.

Relation between size of compound sensory or muscle action potentials, and length of nerve segment

In 24 median nerves from 12 healthy subjects, antidromic digital sensory potentials progressively diminished in size, averaging 40.4,37.0, 30.7, and 23.9 μV × msec with stimulation at the palm, wrist, elbow, and axilla, respectively. In contrast, compound muscle action potentials changed minimally, measuring 19.4, 19.8,19.0, and 18.2 mV × msec, respectively. Similar studies of the ulnar and radial nerves showed identical trends. Physiologic temporal dispersion can mimic conduction block of sensory nerves by summating the peaks of opposite polarity generated by fast- and slow-conducting axons. This type of cancellation affects muscle responses much less because motor unit potentials of longer duration superimpose nearly in phase, given the same latency shift as the sensory potentials.

Dissociation of muscle action potentials and spinal somatosensory evoked potentials after ischemic damage of spinal cord.

In patients undergoing spinal fusion and Cotrel-Dubousset instrumentation we recorded compound muscle action potentials (CMAP) from the lower limb and spinal somatosensory evoked potentials (SSEP) from the caudal epidural space after direct stimulation of rostral spinal cord via epidural electrodes. In three of 30 patients tested, the derotation maneuver altered CMAP but not SSEP. In ten dogs, we observed similar dissociation with decrease or disappearance of CMAP amplitude and unchanged SSEP after ligation of the thoracoabdominal aorta or intercostal arteries at each level. In contrast, both CMAP and SSEP were unchanged by clamping the artery at the lumbar level. This is likely due to the lack of collateral vascular flow at the thoracic cord level, the anterior cord in particular, which is mainly supplied by a single large radicular artery (Adamklewicz artery). These findings support that the CMAP and SSEP are mediated through two independent pathways located in the anterior and posterior spinal cord, respectively. We postulate that the dissociate alteration of CMAP and SSEP by derotation maneuver is due to greater vulnerability of the anterior cord or motor tract to Ischemia caused by the displacement of anterior spinal or radiculomedullary artery. Therefore, the patients requiring major derotation procedure would benefit from CMAP monitoring, which provides more sensitive measure of anterior cord function that the conventional SSEP monitoring.

Experimental scoliosis in melatonin‐deficient C57BL/6J mice without pinealectomy

Abstract:  The etiology of idiopathic scoliosis is unknown. Scoliosis with many characteristics closely resembling those seen in idiopathic scoliosis has been produced in young chickens and bipedal rats after pinealectomy. In this study, we induced experimental scoliosis in C57BL/6J mice without pinealectomy and melatonin treatment suppressed the development of scoliosis. A total of 100 mice were divided into four groups: 20 quadrupedal mice served as controls; 30 mice underwent resection of two forelegs and tail at 3 wk of age (bipedal mice); the remaining 20 quadrupedal and 30 bipedal mice received intraperitoneal melatonin (8 mg/kg BW) at 19:00 hr daily. Before killing, blood samples were collected in the middle of dark cycle and melatonin levels were measured by radioimmunoassay. Spine X‐ray and helical 3D‐CT were examined after killing at 5 months of age. The bipedal mice without a tail were able to walk with standing posture, whereas the quadrupedal mice did not walk with standing posture. In C57BL/6J mice, the serum melatonin was reduced to nearly zero; however, the normal level was restored in both bipedal and quadrupedal mice after the injection of melatonin. Scoliosis with rib humps developed in 29 of 30 bipedal and in five quadrupedal mice. None of mice with melatonin treatment developed scoliosis. The results suggest that melatonin deficiency in bipedal mice appears to play crucial role for development of scoliosis. Also the restoration of melatonin levels prevents the development of scoliosis.

Role of serotonin for scoliotic deformity in pinealectomized chicken.

Study Design. The effect of intraperitoneal injection of 5-hydroxytryptophan (5-HTP) versus control in pinealectomized chickens. Objective. To find if the serotonin may have some role in the cause or treatment of idiopathic scoliosis. Summary of Background Data. One of the causes of idiopathic scoliosis is thought to be the disruption of postural reflex. Serotonin has been proposed to have a crucial role in maintaining normal postural muscle tone or postural equilibrium. Method. Forty pinealectomized chickens served as controls, and an additional 40 pinealectomized chickens received daily intraperitoneal injections of 5-hydroxy-tryptophan, a precursor of serotonin, which can pass through the blood-brain barrier. Spine radiographs were examined to measure the scoliotic deformity. Results. Scoliosis developed in all 40 pinealectomized chickens (control), whereas only 28 chickens in the 5-hydroxytryptophan-treated group (6 in severe, 22 in mild) had scoliosis developed. The remaining 12 chickens grew up with normal spines. Most chickens with mild scoliosis did not have curve progression but continued to have wedged vertebrae. Conclusion. Serotonin deficit secondary to a defect of melatonin may have disturbed postural muscle tone or postural equilibrium resulting in scoliosis in pinealectomized chicken. Prevention from the development of scoliosis or its progression in chickens treated with 5-hydroxytryptophan suggests that serotonin may have potential therapeutic value.