Y. L. Chan

Relative anterior spinal overgrowth in adolescent idiopathic scoliosis: RESULTS OF DISPROPORTIONATE ENDOCHONDRAL-MEMBRANOUS BONE GROWTH

There is no generally accepted scientific theory for the etiology of adolescent idiopathic scoliosis (AIS). As part of its mission to widen understanding of scoliosis etiology, the International Federated Body on Scoliosis Etiology (IBSE) introduced the electronic focus group (EFG) as a means of increasing debate on knowledge of important topics. This has been designated as an on-line Delphi discussion. The text for this EFG was written by Professor Jack Cheng and his colleagues who used whole spine magnetic resonance imaging (MRI) to re-investigate the relative anterior spinal overgrowth of progressive AIS in a cross-sectional study. The text is drawn from research carried out with his co-workers including measurement of the height of vertebral components anteriorly (vertebral body) and posteriorly (pedicles) in girls with AIS and in normal subjects. The findings confirm previous anatomical studies and support the consensus view that in patients with thoracic AIS there is relatively faster growth of anterior and slower growth of posterior elements of thoracic vertebrae. The disproportionate anteroposterior vertebral size is associated with severity of the scoliotic curves. In interpretating the findings they consider the Roth/Porter hypothesis of uncoupled neuro-osseous growth in the spine but point out that knowledge of normal vertebral growth supports the view that the scoliosis deformity in AIS is related to longitudinal vertebral body growth rather than growth of the canal. In the mechanical mechanism (pathomechanism) they implicitly adopt the concept of primary skeletal change as it affects the sagittal plane of the spine with anterior increments and posterior decrements of vertebral growth and, in the biological mechanism (pathogenesis) propose a novel histogenetic hypothesis of uncoupled endochondral-membranous bone formation. The latter is viewed as part of an ‘intrinsic abnormality of skeletal growth in patients with AIS which may be genetic’. The hypothesis that AIS girls have intrinsic anomalies (not abnormalities) of skeletal growth related to curve progression and involving genetic and/or environmental factors acting in early life is not original. While the findings of Professor Cheng and his colleagues have added MRI data to the field of relative anterior spinal overgrowth in AIS their interpretation engenders controversy. Three new hypotheses are proposed to interpret their findings: (1) hypoplasia of articular processes as a risk factor for AIS; (2) selection from the normal population to AIS involves anomalous vertebral morphology and soft tissue factors—this hypothesis may also apply to certain types of secondary scoliosis; and (3) a new method to predict the natural history of AIS curves by evaluating cerebro-spinal fluid (CSF) motion at the cranio–cervical junction. What is not controversial is the need for whole spine MRI research on subjects with non-idiopathic scoliosis.

Relative anterior spinal overgrowth in adolescent idiopathic scoliosis

There is no generally accepted scientific theory for the etiology of adolescent idiopathic scoliosis (AIS). As part of its mission to widen understanding of scoliosis etiology, the International Federated Body on Scoliosis Etiology (IBSE) introduced the electronic focus group (EFG) as a means of increasing debate on knowledge of important topics. This has been designated as an on-line Delphi discussion. The text for this EFG was written by Professor Jack Cheng and his colleagues who used whole spine magnetic resonance imaging (MRI) to re-investigate the relative anterior spinal overgrowth of progressive AIS in a cross-sectional study. The text is drawn from research carried out with his co-workers including measurement of the height of vertebral components anteriorly (vertebral body) and posteriorly (pedicles) in girls with AIS and in normal subjects. The findings confirm previous anatomical studies and support the consensus view that in patients with thoracic AIS there is relatively faster growth of anterior and slower growth of posterior elements of thoracic vertebrae. The disproportionate anteroposterior vertebral size is associated with severity of the scoliotic curves. In interpretating the findings they consider the Roth/Porter hypothesis of uncoupled neuro-osseous growth in the spine but point out that knowledge of normal vertebral growth supports the view that the scoliosis deformity in AIS is related to longitudinal vertebral body growth rather than growth of the canal. In the mechanical mechanism (pathomechanism) they implicitly adopt the concept of primary skeletal change as it affects the sagittal plane of the spine with anterior increments and posterior decrements of vertebral growth and, in the biological mechanism (pathogenesis) propose a novel histogenetic hypothesis of uncoupled endochondral-membranous bone formation. The latter is viewed as part of an ‘intrinsic abnormality of skeletal growth in patients with AIS which may be genetic’. The hypothesis that AIS girls have intrinsic anomalies (not abnormalities) of skeletal growth related to curve progression and involving genetic and/or environmental factors acting in early life is not original. While the findings of Professor Cheng and his colleagues have added MRI data to the field of relative anterior spinal overgrowth in AIS their interpretation engenders controversy. Three new hypotheses are proposed to interpret their findings: (1) hypoplasia of articular processes as a risk factor for AIS; (2) selection from the normal population to AIS involves anomalous vertebral morphology and soft tissue factors—this hypothesis may also apply to certain types of secondary scoliosis; and (3) a new method to predict the natural history of AIS curves by evaluating cerebro-spinal fluid (CSF) motion at the cranio–cervical junction. What is not controversial is the need for whole spine MRI research on subjects with non-idiopathic scoliosis.

Sonographic measurement of mesenteric fat thickness is a good correlate with cardiovascular risk factors: comparison with subcutaneous and preperitoneal fat thickness, magnetic resonance imaging and anthropometric indexes

OBJECTIVE: Visceral fat, notably mesenteric fat, which is drained by the portal circulation, plays a critical role in the pathogenesis of metabolic syndrome through increased production of free fatty acids, cytokines and vasoactive peptides. We hypothesize that mesenteric fat thickness as measured by ultrasound scan could explain most of the obesity-related health risk. We explored the relationships between cardiovascular risk factors and abdominal fat as determined by sonographic measurements of thickness of mesenteric, preperitoneal and subcutaneous fat deposits, total abdominal and visceral fat measurement by magnetic resonance imaging (MRI) and anthropometric indexes.DESIGN: A cross-sectional study.SUBJECTS: Subjects included 18 healthy men and 19 women (age: 27–61 y, BMI: 19–33.4 kg/m2).MEASUREMENTS: The maximum thickness of mesenteric, preperitoneal and subcutaneous fat was measured by abdominal ultrasound examination. MRI examinations of whole abdomen and pelvis were performed and the amount of total abdominal and visceral fat was quantified. The body mass index, waist circumference and waist–hip ratio were recorded. Cardiovascular risk factors were assessed by physical examination and blood taking.RESULTS: Men had more adverse cardiovascular risk profile, higher visceral fat volume and thicker mesenteric fat deposits than women. Among all the investigated obesity indexes, the mesenteric fat thickness showed the highest correlations with total cholesterol, LDL-C, triglycerides, fasting plasma glucose, HbA1c and systolic blood pressure in men, and with triglycerides and HbA1c in women. On stepwise multiple regression analysis with different obesity indexes as independent variables, 30–65% of the variances of triglycerides, total cholesterol, LDL-C and HbA1c in men, and triglycerides in women were explained by the mesenteric fat thickness.CONCLUSION: Compared with sonographic measurement of subcutaneous and preperitoneal fat thickness, MRI measurement of total abdominal and visceral fat and anthropometric indexes, sonographic measurement of mesenteric fat thickness showed better associations with some of the cardiovascular risk factors. It may potentially be a useful tool to evaluate regional distribution of obesity in the assessment of cardiovascular risk.

Correlation between curve severity, somatosensory evoked potentials, and magnetic resonance imaging in adolescent idiopathic scoliosis.

STUDY DESIGN A prospective study in patients with adolescent idiopathic scoliosis of different clinical severity using whole-spine magnetic resonance imaging and somatosensory evoked potentials. OBJECTIVES To correlate the presence of magnetic resonance imaging structural abnormalities with somatosensory evoked potential-detected functional disorders in the hind brain and spinal cord and the Cobbs angle in patients with adolescent idiopathic scoliosis and to compare the result with those in healthy matched control subjects. SUMMARY OF BACKGROUND DATA Many different types of neurologic dysfunction have been reported in scoliosis. With the advent of magnetic resonance imaging, there are increased reports on the association of idiopathic scoliosis and syringomyelia, Chiari I malformation, or tonsillar ectopia. The actual link between structural and functional disorder in idiopathic scoliosis is, however, unclear. METHODS Posterior tibial nerve evoked potentials and whole-spine magnetic resonance imaging were performed in 36 healthy control subjects, 135 patients with adolescent idiopathic scoliosis with Cobbs angle less than 45 degrees, and 29 patients with Cobbs angle more than 45 degrees. RESULTS Tonsillar ectopia or syringomyelia, detected by magnetic resonance imaging, or functional disturbance in the somatosensory pathway, detected by somatosensory evoked potentials, was found to be significantly more frequent in the group of patients with severe scoliosis curvature, with an incidence of 31% and 27.6%, respectively. Incidence of tonsillar ectopia was 33.3% in patients with abnormal somatosensory evoked potentials in contrast to the much lower incidence of 2.9% in patients with normal somatosensory evoked potentials. There was a significant structural and functional link. The incidence of syringomyelia in patients with and without tonsillar ectopia was 33.3% and 0.7%, respectively. CONCLUSIONS In patients with adolescent idiopathic scoliosis with severe curve, the significant association with tonsillar ectopia and abnormal somatosensory function points to a neural origin. Disorders in the somatosensory function may be one of the mechanisms linking tonsillar ectopia to scoliosis. Somatosensory evoked potentials and magnetic resonance imaging may have important diagnostic and predictive value and may help in the management of adolescent idiopathic scoliosis.

Relative shortening and functional tethering of spinal cord in adolescent idiopathic scoliosis?: study with multiplanar reformat magnetic resonance imaging and somatosensory evoked potential.

Study Design. MR imaging and multiplanar reconstruction were used to evaluate relative length of the spinal cord to the vertebral column in adolescent idiopathic scoliosis (AIS). Objectives. Ratio of spinal cord length to vertebral column length and position of the cerebellar tonsils were evaluated and correlated with somatosensory cortical evoked potentials (SSEP). Summary of Background Data. Tonsillar herniation, abnormal anthropometric growth, relative spinal overgrowth, and abnormal somatosensory function have been reported in AIS. All these observations suggest a possible neural origin of the etiopathogenesis of AIS, which can be linked to a disproportional growth between spinal column and cord. Methods. Two-dimensional sagittal MRI of the spine was performed in 28 AIS patients (14 mild curve; 14 severe curve) and 14 age-matched controls. Measurements of spinal cord, vertebral column length, and tonsillar position were made on reformat images and correlated with SSEP studies. Results. No significant differences in the absolute spinal cord length were found. However, there was significant relative segmental lengthening of the spinal column at the thoracic level in AIS patients with severe curve; hence, ratios of cord to vertebral column length were significantly reduced (P < 0.01). There was high interobserver reliability (0.9); 28% (8 of 28) scoliosis patients had low-lying cerebellar tonsils and abnormal SSEP, respectively. Conclusion. There was significantly reduced spinal cord to vertebral column ratios in the AIS patients with severe curve, suggesting a disproportional growth between the skeletal and the neural systems. The relative shortening and functional tethering of spinal cord may play an important role in the etiopathogenesis of AIS.

A new management algorithm for impalpable undescended testis with gadolinium enhanced magnetic resonance angiography.

PURPOSE We evaluated the diagnostic accuracy of preoperative localization of impalpable undescended testis using ultrasound and gadolinium (Gd) enhanced magnetic resonance angiography (MRA). MATERIALS AND METHODS Ultrasound and Gd-MRA were performed prospectively in 21 boys (23 impalpable testes) with cryptorchidism before laparoscopy and surgical exploration. Gd-MRA was done using a 1.5 Tesla magnetic resonance scanner with a turbo field echo technique after bolus intravenous injection of 0.4 mmol./kg. body weight of Gd diethylenetriaminepentaacetic acid. A total of 10 dynamic scans were acquired during 15 minutes after Gd injection to cover the early arterial and delayed venous phases. All patients subsequently underwent diagnostic laparoscopy and definitive surgery. RESULTS Ultrasound correctly localized 9 of 10 intracanalicular testes but failed to reveal any intra-abdominal or vanishing testes. In contrast, Gd-MRA correctly localized 4 intra-abdominal, all 10 intracanalicular and 8 canalicular vanishing testes. In 1 patient with an intra-abdominal vanishing testis ultrasound and Gd-MRA failed to make the diagnosis. When correlated with the findings of subsequent laparoscopy and surgical exploration, Gd-MRA had a diagnostic sensitivity of 96% and a specificity of 100% for localizing impalpable undescended testes. Based on Gd-MRA and ultrasound findings laparoscopy could have been avoided in 18 of 23 cases (78%). No adverse effect was associated with Gd use in this study. CONCLUSIONS Gd-MRA accurately diagnoses vanishing testes and reliably differentiates intraabdominal from intracanalicular impalpable testes, allowing definite preoperative planning of the surgical approach and avoiding unnecessary laparoscopy. A new management algorithm for impalpable testis in patients with cryptorchidism is proposed based on ultrasound and Gd-MRA findings.

Visceral Fat and Cardiovascular Risk Factors in Chinese NIDDM Patients

OBJECTIVE The interrelations between obesity, glucose intolerance, hypertension, dyslipidemia, and insulin resistance are well recognized. These relationships are of particular interest in Hong Kongs Chinese population, in whom increasing affluence has coincided with a marked increase in the prevalence of NIDDM. We designed a pilot study to examine the relationships between visceral fat and cardiovascular risk factors in Chinese NIDDM patients. RESEARCH DESIGN AND METHODS We studied 21 Chinese NIDDM patients whose visceral fat was quantified by magnetic resonance imaging. Cardiovascular risk factors including plasma lipids and 24-h ambulatory blood pressure (BP) were measured. In addition, insulin resistance was determined by a short insulin tolerance test (SITT). RESULTS Increased visceral adiposity was significantly correlated with plasma triglycerides (r = 0.63, P = 0.004), the total cholesterol/HDL cholesterol ratio (r = 0.61, P = 0.008), the urinary albumin/creatinine ratio (r = 0.49, P = 0.04), and decreased insulin sensitivity as measured by the SITT (r = 0.47, P = 0.03). When the data were analyzed by tertiles, increasing visceral fat area was associated with higher plasma triglycerides, lower HDL cholesterol, and a smaller plasma glucose decrement during the SITT. In addition, the diurnal rhythm in BP and heart rate tended to be best preserved in those with the least visceral obesity. CONCLUSIONS This pilot study demonstrates that visceral fat accumulation is associated with dyslipidemia, hypertension, insulin resistance, and albuminuria in Chinese patients with NIDDM.

Retropharyngeal lymphadenopathy in nasopharyngeal carcinoma

Background This study was done to investigate the size of normal retropharyngeal lymph nodes (RLN) and the incidence of retropharyngeal lymph node involvement in patients with nasopharyngyngeal carcinoma (NPC). Methods Forty-four NPC patients who had not yet received treatment and 20 control subjects underwent MRI scanning. The number and the maximum diameter of the short axis of the cervical lymph nodes were measured. The number of nasopharyngeal walls involved and the maximum diameter of the tumor were recorded. Results In 5 of 20 control subjects lateral RLN were identified; none of these nodes was greater than 2.5 mm. In the NPC patients, taking 4 mm as the upper limit of normal RLN, 89% of the patients had enlarged RLN. The number of nasopharyngeal walls involved and the maximum diameter of the primary tumor showed no statistical relationship with the involvement of RLN. There was a statistical association between RLN and level II node involvement, but not with other groups of neck nodes. Conclusion Of all patients with NPC, 89% showed enlarged RLN. Its involvement was related to level II nodes but not to the number of nasopharyngeal sites involved nor with the maximum diameter of the tumor.

Ultrasonography of congenital muscular torticollis

The sonographic appearance of the sternocleidomastoid muscles of 36 children with congenital muscular torticollis was studied. Sternocleidomastoid tumour was detected in all of them and the images were more complex than described in the literature. A patchy echotexture was as frequent as a homogeneous echo-texture, and was more common in the younger child. The echogenicity of the mass could be hyperechoic, isoechoic or hypoechoic relative to normal muscle. A hypoechoic rim surrounding the mass was frequently present. Change of the proportion of the mass relative to the entire musclemass complex in different ages matching clinical observations was also noted. These sonographic findings would be important in establishing a sonographic diagnosis. The higher sensitivity of ultrasound in detection of sternocleidomastoid tumour over clinical methods, and the importance of the sonographic findings in the management of congenital muscular torticollis were also discussed.

Relative anterior spinal overgrowth in adolescent idiopathic scoliosis—result of disproportionate endochondral-membranous bone growth?

There is no generally accepted scientific theory for the etiology of adolescent idiopathic scoliosis (AIS). As part of its mission to widen understanding of scoliosis etiology, the International Federated Body on Scoliosis Etiology (IBSE) introduced the electronic focus group (EFG) as a means of increasing debate on knowledge of important topics. This has been designated as an on-line Delphi discussion. The text for this EFG was written by Professor Jack Cheng and his colleagues who used whole spine magnetic resonance imaging (MRI) to re-investigate the relative anterior spinal overgrowth of progressive AIS in a cross-sectional study. The text is drawn from research carried out with his co-workers including measurement of the height of vertebral components anteriorly (vertebral body) and posteriorly (pedicles) in girls with AIS and in normal subjects. The findings confirm previous anatomical studies and support the consensus view that in patients with thoracic AIS there is relatively faster growth of anterior and slower growth of posterior elements of thoracic vertebrae. The disproportionate anteroposterior vertebral size is associated with severity of the scoliotic curves. In interpretating the findings they consider the Roth/Porter hypothesis of uncoupled neuro-osseous growth in the spine but point out that knowledge of normal vertebral growth supports the view that the scoliosis deformity in AIS is related to longitudinal vertebral body growth rather than growth of the canal. In the mechanical mechanism (pathomechanism) they implicitly adopt the concept of primary skeletal change as it affects the sagittal plane of the spine with anterior increments and posterior decrements of vertebral growth and, in the biological mechanism (pathogenesis) propose a novel histogenetic hypothesis of uncoupled endochondral-membranous bone formation. The latter is viewed as part of an ‘intrinsic abnormality of skeletal growth in patients with AIS which may be genetic’. The hypothesis that AIS girls have intrinsic anomalies (not abnormalities) of skeletal growth related to curve progression and involving genetic and/or environmental factors acting in early life is not original. While the findings of Professor Cheng and his colleagues have added MRI data to the field of relative anterior spinal overgrowth in AIS their interpretation engenders controversy. Three new hypotheses are proposed to interpret their findings: (1) hypoplasia of articular processes as a risk factor for AIS; (2) selection from the normal population to AIS involves anomalous vertebral morphology and soft tissue factors—this hypothesis may also apply to certain types of secondary scoliosis; and (3) a new method to predict the natural history of AIS curves by evaluating cerebro-spinal fluid (CSF) motion at the cranio–cervical junction. What is not controversial is the need for whole spine MRI research on subjects with non-idiopathic scoliosis.