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Post-publication Peer Reviews to:
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![[Read P3R]](/icons/misc/sectionDOWN.gif){kind=icon}
Changes to the algorithm for evaluating spinal dimples
Response to Letter from Mark S. Dias, MD dated January 8,2002
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Mark S. Dias, Pediatric Neurosurgeon Section of Pediatric Neurosurgery, Penn State Milton S. Hershey Medical Center
Send letter to journal:
mdias{at}psu.edu Mark S. Dias
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I read with interest the article “Newborns with suspected occult spinal dysraphism: A cost-effectiveness analysis of diagnostic strategies” by Medina LS, Crone K, and Kuntz KM, which appeared in Pediatrics 108(6):e101 (2001). Although I agree with the majority of the authors’ recommendations, I would take issue with two points regarding the management of dermal sinus tracts. First, the authors suggest that a child with an innocent coccygeal (intergluteal) dimple carries a 0.34% risk of harboring an intraspinal occult dysraphic malformation and recommend that such children could be followed either with clinical evaluation or with ultrasound. This is an ambiguous recommendation for a very large group of children. If these children could be followed clinically, then what would make them candidates for ultrasound? If, on the other hand, there is a true risk of underlying intraspinal pathology, then why wouldn’t the authors recommend ultrasound for the entire group? Innocent uncomplicated coccygeal dimples, located within the gluteal cleft, are present in 3-5% of the population, and there is no evidence that these children harbor underlying spinal cord malformations any more frequently than the general population. A recent article by Weprin and Oakes (1), appearing in the May 2000 issue of Pediatrics (just after the present paper had been accepted for publication), thoroughly reviewed the medical literature on these coccygeal dimples, or ‘pits’, and identified only 7 previously reported cases with underlying intraspinal pathology. Of these, 5 patients had other cutaneous stigmata of spinal dysraphism (such as additional more rostrally situated dimples and/or hemangiomas) that would otherwise have suggested a dysraphic condition and in whom the coccygeal dimple may have been purely a coincidental finding. The dimples in the two remaining patients had not been sufficiently described to adequately determine their exact location. Weprin and Oakes also reviewed their own personal series of 1000 coccygeal dimples followed sequentially, with none developing any signs or symptoms of meningitis, tethering or other neurological deterioration attributable to occult dysraphism. They concluded all that is necessary for this group of children is a clinical evaluation. I would also take issue with the authors’ algorithm that allows for ‘clinical follow-up’ of patients with moderate or high risk lumbosacral dimples. The authors estimate the sensitivity of MRI to be 95.6% based upon 2 studies. In my own experience at three separate academic institutions, the sensitivity of MRI is significantly less, and I have operated on several dermal sinuses having intrathecal extension in the face of completely normal MRI scans. Unfortunately, there are significant and potentially fatal consequences of missing a dermal sinus tract that communicates with the lumbar theca, the most important being bacterial meningitis. The MRI is obtained, not to rule out intrathecal extension, but to identify and characterize both the anatomy of the sinus and any co- existing dysraphic anomalies that might be present. For all of these reasons, both myself and all pediatric neurosurgeons with whom I’ve spoken explore and repair lumbosacral sinus tracts regardless of the findings on imaging studies. The sinus that terminates superficial to the lumbodorsal fascia requires only a superficial excision of the dimple. On the other hand, the sinus tract that traverses the fascia - typically piercing the lumbodorsal dura, traversing the subarachnoid space, and attaching to the dorsal aspect of the conus medullaris - should be followed down to its terminus and excised. I would therefore suggest a more medically appropriate, and more cost -effective, scheme for evaluating these sinus tracts. For the 3-5% of children having an isolated coccygeal dimple (one within the gluteal cleft and overlying the tip of the coccyx), nothing more need be done except to reassure the parents. The money saved by avoiding any imaging study in this large group can be more appropriately applied to the much smaller group with dimples that lie above the gluteal cleft (including all of those in the medium and high risk groups), to obtain an MRI to appropriately define and characterize the anatomy in preparation for surgery. Mark S. Dias, MD, FAAP Section of Pediatric Neurosurgery Penn State Milton S. Hershey Medical Center Hershey PA References 1. Weprin LS, BE, Oakes WJ. Coccygeal pits. Pediatrics 105(5): E69 (2000) |
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L. Santiago Medina, MD, MPH, Neuroradiologist Miami Children's Hospital Dept. of Radiology, Kerry Crone, MD, Karen M. Kuntz, ScD
Send letter to journal:
smedina{at}post.harvard.edu L. Santiago Medina, MD, MPH, et al.
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I am writing the following letter in response to the letter from Mark S. Dias MD dated January 8, 2002 (copy of the letter enclosed below). Our article “Newborns With Suspected Occult Spinal Dysraphism: A Cost -Effectiveness Analysis of Diagnostic Strategies L. Santiago Medina, Kerry Crone, and Karen M. Kuntz Pediatrics 2001; 108: 101 (Electronic Articles) http://www.pediatrics.org//cgi/content/abstract/108/6/e101 http://www.pediatrics.org//cgi/content/full/108/6/e101 “ discusses the following important points about the low risk group. First, the prevalence (pretest probability) of a dysraphic lesion among children with low intergluteal dimples has been estimated at 0.34% (3.4 per 1000) according to the article by Herman et al. (1). We performed a cost- effectiveness analysis for this risk group using life expectancy as an outcome and found that no imaging costs less and improved life expectancy compared with all other strategies. When we incorporated adjustments for health-related quality of life we found that ultrasound offered a greater effectiveness at an incremental cost-effectiveness ratio of $55,100 per quality-adjusted year of life gained. Based on these results, therefore, we recommended for this low risk group, the strategies of ultrasound or no imaging, depending on how much society is willing to spend on a life year or quality-adjusted life year gained. We do not feel that this recommendation is ambiguous, but that it highlights the tradeoff between the utilization of scarce resources and realizing potentially small health gains. If, however, the pretest probability of a dysraphic lesion among children with low intergluteal dimples was 0%, as Dr. Dias asserts based on the article by Weprin and Oakes (2), then there is no disease to be potentially detected by imaging. In this case, no imaging or other diagnostic test is warranted. The recommendation, therefore, would certainly be the one proposed by Dr. Dias. The option for ‘clinical follow-up’ of patients with moderate or high risk lumbosacral dimples was included for the sake of completeness in our analysis. We agree with Dr. Dias that it is not a viable option for children at higher risk, as was bourn out in our analysis. Our estimate of the sensitivity of MRI was based on published evidence. We recognize that there may be limitations because of publication bias, which is why we reported extensive sensitivity analysis on this estimate. L. Santiago Medina, MD, MPH Neuroradiologist Director,Health Outcomes, Policy and Economics (HOPE)Center Department of Radiology- Miami Children's Hospital 3100 SW 62 Ave Miami, FL 33155 305 669 6482 fax 305 669 6580 e-mail: smedina@post.harvard.edu Kerry Crone, MD Director, Division of Neurosurgery Children’s Hospital Medical Center Cincinnati, Ohio Karen M. Kuntz, ScD Center for Risk Analysis Harvard School of Public Health 718 Huntington Avenue Boston, MA 02115 References: 1. Herman TE, Oser RF, Shackelford GD. Intergluteal dorsal dermal sinuses. The role of neonatal spinal sonography. Clin Pediatr. 1993;32:627 -628. 2. Weprin BE, Oakes WJ. Coccygeal pits. Pediatrics 2000;105(5): E69 An electronic letter was submitted from Pediatrics Online's Post Publication Peer Review for your article. It is our intention to post this letter on the web site and we would like your feedback on the letter. Your article (citation): Newborns With Suspected Occult Spinal Dysraphism: A Cost- Effectiveness Analysis of Diagnostic Strategies L. Santiago Medina, Kerry Crone, and Karen M. Kuntz Pediatrics 2001; 108: 101 (Electronic Articles) http://www.pediatrics.org//cgi/content/abstract/108/6/e101 http://www.pediatrics.org//cgi/content/full/108/6/e101 The letter was submitted on 8 Jan 2002: Name: Mark S. Dias Email: mdias@psu.edu Title/position: Pediatric Neurosurgeon Place of work: Section of Pediatric Neurosurgery, Penn State Milton S. Hershey Medical Center Title: "Changes to the algorithm for evaluating spinal dimples" Contents: <!-- article ID: pediatrics;108/6/e101 --> <P> I read with interest the article “Newborns with suspected occult spinal dysraphism: A cost-effectiveness analysis of diagnostic strategies” by Medina LS, Crone K, and Kuntz KM, which appeared in Pediatrics 108(6):e101 (2001). Although I agree with the majority of the authors’ recommendations, I would take issue with two points regarding the management of dermal sinus tracts. <P> First, the authors suggest that a child with an innocent coccygeal (intergluteal) dimple carries a 0.34% risk of harboring an intraspinal occult dysraphic malformation and recommend that such children could be followed either with clinical evaluation or with ultrasound. This is an ambiguous recommendation for a very large group of children. If these children could be followed clinically, then what would make them candidates for ultrasound? If, on the other hand, there is a true risk of underlying intraspinal pathology, then why wouldn’t the authors recommend ultrasound for the entire group? <P> Innocent uncomplicated coccygeal dimples, located within the gluteal cleft, are present in 3-5% of the population, and there is no evidence that these children harbor underlying spinal cord malformations any more frequently than the general population. A recent article by Weprin and Oakes (1), appearing in the May 2000 issue of Pediatrics (just after the present paper had been accepted for publication), thoroughly reviewed the medical literature on these coccygeal dimples, or ‘pits’, and identified only 7 previously reported cases with underlying intraspinal pathology. Of these, 5 patients had other cutaneous stigmata of spinal dysraphism (such as additional more rostrally situated dimples and/or hemangiomas) that would otherwise have suggested a dysraphic condition and in whom the coccygeal dimple may have been purely a coincidental finding. The dimples in the two remaining patients had not been sufficiently described to adequately determine their exact location. Weprin and Oakes also reviewed their own personal series of 1000 coccygeal dimples followed sequentially, with none developing any signs or symptoms of meningitis, tethering or other neurological deterioration attributable to occult dysraphism. They concluded all that is necessary for this group of children is a clinical evaluation. <P> I would also take issue with the authors’ algorithm that allows for ‘clinical follow-up’ of patients with moderate or high risk lumbosacral dimples. The authors estimate the sensitivity of MRI to be 95.6% based upon 2 studies. In my own experience at three separate academic institutions, the sensitivity of MRI is significantly less, and I have operated on several dermal sinuses having intrathecal extension in the face of completely normal MRI scans. Unfortunately, there are significant and potentially fatal consequences of missing a dermal sinus tract that communicates with the lumbar theca, the most important being bacterial meningitis. The MRI is obtained, not to rule out intrathecal extension, but to identify and characterize both the anatomy of the sinus and any co- existing dysraphic anomalies that might be present. <P> For all of these reasons, both myself and all pediatric neurosurgeons with whom I’ve spoken explore and repair lumbosacral sinus tracts regardless of the findings on imaging studies. The sinus that terminates superficial to the lumbodorsal fascia requires only a superficial excision of the dimple. On the other hand, the sinus tract that traverses the fascia - typically piercing the lumbodorsal dura, traversing the subarachnoid space, and attaching to the dorsal aspect of the conus medullaris - should be followed down to its terminus and excised. <P> I would therefore suggest a more medically appropriate, and more cost -effective, scheme for evaluating these sinus tracts. For the 3-5% of children having an isolated coccygeal dimple (one within the gluteal cleft and overlying the tip of the coccyx), nothing more need be done except to reassure the parents. The money saved by avoiding any imaging study in this large group can be more appropriately applied to the much smaller group with dimples that lie above the gluteal cleft (including all of those in the medium and high risk groups), to obtain an MRI to appropriately define and characterize the anatomy in preparation for surgery. <P> Mark S. Dias, MD, FAAP Section of Pediatric Neurosurgery Penn State Milton S. Hershey Medical Center Hershey PA <P> References <P> 1. Weprin LS, BE, Oakes WJ. Coccygeal pits. Pediatrics 105(5): E69 (2000) If you would like to have a response to this letter, please use the P3R function on your article "Submit a response" link in the content box at the upper right of your article's page. Please let us know if you have any other questions or reactions to this process. Thank you. Sincerely, The Editorial Staff of "Pediatrics" |
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