neurofibromatosis type - i ( nf-1 , von recklinghausen 's disease ) is an autosomal - dominant single - gene hereditary disorder of neural crest cells , involving neuroectoderm , mesoderm , and endoderm . it affects 1:3000 - 4000 individuals and is caused by a defect in the gene responsible for the production of the protein neurofibromin : the nf-1 gene . the nf-1 gene is a tumor suppressor gene linked to the long arm of chromosome 17 . the clinical manifestations of nf-1 are as follows : caf - au - lait spots , axillary or inguinal freckling , lisch nodules of the iris , neurofibromas , optic gliomas , and spinal skeletal deformities . the latter manifest as acquired short , sharp , and angular ( usually thoracic ) scoliotic curves . dystrophic changes such as rib - penciling , vertebral scalloping , transverse process spindling , apical wedging , foraminal enlargement , and dural ectasia are classic features various procedures have been reported and entail anterior , posterior , and combined anterior / posterior approaches to establish arthrodesis and prevent curve progression . we describe a case that highlights the operative management of an nf-1 patient with severe dystrophic thoracic kyphoscoliosis treated by a posterolateral spinal approach . a 44-year - old patient with nf-1 presented to the department of neurosurgery with myelopathy caused by a 93 thoracic ( t5-t9 ) kyphoscoliosis , thoracic vertebral scalloping leading to a severe thinning of the vertebral bodies , profound stenosis by a bony ridge between two dural ectasias at t4-t5 anteriorly and auto fusion of t4-t7 [ figures 1 and 2 ] . magnetic resonance image of a 93 thoracic kyphoscoliosis and stenosis due to a bony ridge ( red circle ) between two dural ectasias at t4-t5 anteriorly and an autofusion of t4-t7 . note the dural ctasias ( asterix ) and the vertebral scalloping ( yellow curve ) computed tomography image of the thoracic spine with a 93 kyphoscoliosis . note the bony anterior autofusion of t4-t7 clinically , she had progressive sensory disturbances and upper motor signs . operative intervention , performed using intraoperative neuromonitoring , consisted of a posterolateral approach with posterior thoracic cord exposure , anterior decompression of the bony ridge on t4-t5 by a right costotransversectomy [ figure 3 ] at t4 and posterior fusion of c6-t12 with bilateral pedicle screws at the c6 , t11 , and t12 level as well as bilateral bridging rod instrumentation [ figures 4 and 5 ] . cadaver view of the anterior thoracic spinal cord with the thoracic nerve root lifted upward ( curved arrow ) after a performed right costotransversectomy at t4 . note the detailed exposure of the anterior spinal cord with its epidural space ( white circle ) , corresponding veins ( black arrow ) , and the posterior longitudinal ligament ( white arrow ) . remark : the spinous process and the lamina have been removed for demonstrative purposes postoperative x - ray image showing the posterior fusion from c6 to t12 with bilateral pedicle screws at the c6 , t11 , and t12 level and bilateral bridging rods postoperative computed tomography image with posterior fusion of c6-t12 . note the pedicle screws at the c6 , t11 , and t12 level as well as the resection of the bony ridge at t4-t5 ( red circle ) it occurs usually in the low thoracic region and has a prevalence ranging from 2% to 69% in the literature . etiological theories regarding nf-1-related scoliosis include erosion or infiltration of bone by neurofibromas , primary mesodermal dysplasia , osteomalacia , and endocrine disturbances . this classification is based on the absence or presence of skeletal dysplasia , such as vertebral scalloping and associated dural ectasias , rib penciling , vertebral wedging , transverse process spindling , paraspinal or intraspinal soft tissue masses , apical rotation , foraminal enlargement , pedicle dysplasia , and widened interpediculate distance . the literature states that the likelihood of curve progression and deterioration is proportional to the severity of skeletal dystrophy . studies have shown that when a combination of three or more dysplastic features are present , the risk of curve deterioration was significantly increased in 85% of patients . non - dystrophic curves can be managed as idiopathic scoliosis , dystrophic curves , however , need a more aggressive approach . a dystrophic curve pattern , as this was the case in our patient , classically presents as a short segment , sharply angulated , thoracic curve with three or more dystrophic elements . they require aggressive treatment as there is a strong tendency for curve progression and clinical catastrophic deterioration . dystrophic scoliosis less than 20 should be closely monitored at 6 month intervals . in scoliosis , measuring 20-40 with less than 50 of kyphosis , a posterior spinal arthrodesis is feasible . however , when the scoliosis exceeds 40 and/or thoracic hyperkyphosis exceeds 50 , a combined anterior / posterior ( circumferential ) fusion is mandatory . neurological deficits are usually caused by hyperkyphosis and subsequent attenuation and deformation of the spinal cord . in those cases , an anterior decompression followed by circumferential fusion other contributory factors include intraspinal tumors , which have to be resected followed by a mechanical stabilization and bony fusion . one of the difficulties encountered in nf - spinal surgery is the segmental instrumentation and fusion as there can be poor anchorage points for internal fixation due to vertebral destruction . due to the high incidence of pseudarthrosis , fusion evaluation should be performed at 6 months and at regular intervals until solid arthrodesis is obtained . in case of failure , the neurological deficit was caused by a 93 thoracic ( t5-t9 ) kyphoscoliosis and stenosis due to a bony ridge between two dural ectasias at t4-t5 anteriorly [ figure 1 ] . furthermore , there was an autofusion of t4-t7 [ figures 1 and 2 ] . due to the anterior t4-t7 autofusion , severe kyphosis , and the presence of dural actasias we choose a posterolateral approach [ figure 3 ] instead with thoracic cord exposure , anterior decompression of the bony ridge on t4-t5 by a right costotransversectomy at t4 and posterior fusion of c6-t12 with bilateral pedicle screws at the c6 , t11 and t12 level as well as bilateral bridging rod instrumentation [ figures 4 and 5 ] . we state that in selected cases of severe thoracic dystrophic kyphoscoliosis in nf - i , the posterolateral approach [ figure 3 ] is the only possible method to visualize the anterior thoracic spinal cord , perform anterior decompression , and to stabilize the thoracic deformity , because of the anterior dural ectasias and the kyphosis limiting an anterior procedure .