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Orthopedics and Sports Medicine Case of the Month

January 2012: Idiopathic Scoliosis?

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Patient History

A healthy 11-year-3-month-old girl presented for evaluation of spinal deformity that had rapidly progressed over the preceding six months. It was noted due to marked asymmetry of her shoulders. She had no back pain, headaches or neurological symptoms; no family history of scoliosis or any neurological disorders.

Physical Examination and Diagnostic Imaging

Chiari 1 Malformation

Chiari 1 malformation: Note the cerebellar tonsils are 7 mm below the foramen magnum, narrowing the space available for normal cerebrospinal fluid (CSF) flow anterior and posterior to the spinal cord. (Figure 1)

Examination showed that she had profound chest wall, waist and shoulder asymmetry. Her forward bend test demonstrated over 20 degrees of right thoracic truncal rotation and 8 degrees of left lumbar truncal rotation, and there was no significant stiffness or unusual motion with forward bending of the spine. There were no abnormal neurological findings on a detailed exam, which included symmetric abdominal reflexes. Posteroanterior (PA) and lateral scoliosis X-rays demonstrated a 71-degree right thoracic scoliosis, with no congenital abnormalities, such as hemivertebrae or fused spinal segments (Figure 1).

Chiari Malformation, Severe Crowding

In another patient you can see the more severe crowding at the foramen magnum and the presence of a large syrinx (fluid cyst within the spinal cord). (Figure 2)

Due to onset of the curvature prior to age 11 and rapid progression of her scoliosis by history, concern was raised for possible intraspinal pathology. An MRI of the spinal cord was ordered. It showed a Chiari 1 malformation with 7 mm of cerebellar tonsillar herniation below the foramen magnum, but no tethering of the cord or syrinx (a fluid cyst within the spinal cord) (Figure 2).

Patient Diagnosis

Idiopathic-like scoliosis associated with Chiari 1 malformation.

Treatment

The treatment plan for this patient included a staged procedure consisting of decompression of the posterior fossa for the Chiari malformation. This was followed by posterior spinal fusion with instrumentation for correction of the rapidly progressive scoliosis. Because her Chiari 1 malformation was substantial and would put her at significant risk of neurological injury during corrective surgery, she was initially referred to the neurosurgical team. A posterior fossa decompression and C1 laminectomy was performed successfully by the neurosurgeons. She had an uncomplicated postoperative course, and two months later underwent a posterior spinal instrumentation and fusion from T4 to L1 for correction of her scoliosis. Because of the known Chiari malformation and the associated risk of increased sensitivity of the spinal cord, care was taken intraoperatively to avoid vigorous corrective maneuvers or excessive lengthening of the spine. Posterior spinal fusion was successfully performed, with neither intraoperative nor postoperative neurological problems noted.

Discussion

Preoperative Scoliosis X-ray

Preoperative scoliosis X-ray: Note rib cage asymmetry and shoulder height asymmetry. (Figure 3)

Idiopathic scoliosis is most common in adolescent girls. A typical evaluation of scoliosis in the office includes a thorough history and physical exam, and standing PA and lateral scoliosis radiographs. MRI is not necessary for patients with typical curve patterns and no neurological symptoms. The majority of scoliosis patients never develop a curve large enough to require surgical intervention (50 to 60 degrees). Bracing is a treatment option for curves between 20 and 45 degrees in the actively growing child, but only lessens the chance of significant curve correction by about half, and does not make the curve go away. Physical therapy, though advocated by many as a treatment modality, has not shown a great effect on lessening the chances of curve progression. Oftentimes, management of scoliosis is expectant, with serial physical and radiographic evaluations performed at four to six month intervals until skeletal maturity is reached.

It is important to recognize when a patient’s presentation is atypical, thus warranting additional evaluation – as with our patient. Specifically, there are some patients with “idiopathic” scoliosis for whom an MRI of the spine is recommended to evaluate for intraspinal pathology as a cause of the scoliosis. Risk factors for the presence of intraspinal pathology are: patients who are 10 years old or younger at the onset of their scoliosis; are male; who have rapid progression of their curve magnitude (we define this as greater than 15 degrees over 6 months); who have a history of neurological symptoms (e.g., occipital headaches or lightheadedness with exertion); who have abnormal findings on physical examination, such as stiffness or unusual motion on forward bend or abnormal neurological findings; and who have atypical curve patterns (specifically, left thoracic curves or kyphosis of the thoracic spine. Typical idiopathic curves are lordotic at the apex of the curve). Patients with one or more of these risk factors should be considered for an MRI to screen for the presence of intraspinal pathology. The most common abnormal findings at the time of MRI are syrinx and Chiari malformation, with tethered cord and intraspinal tumor being more rarely encountered. In one series of patients with “idiopathic scoliosis” undergoing routine spinal MRI, 4.2% of patients were found to have intraspinal abnormality. When an abnormality is present, 67% of time it is a syrinx, 30% are Chiari 1 malformations and 3% tethered cords. Approximately 30% to 50% of patients with Chiari 1 will have associated scoliosis.

On a technical note, the presence of intraspinal pathology increases the risk of spinal cord injury during scoliosis correction, particularly Chiari malformation with a large syrinx or tethered cord, due to the lengthening effect of the surgery. Having knowledge of the presence of these abnormalities is therefor extremely important for surgical planning.

Outcome

Postoperative Scoliosis X-ray

Postoperative scoliosis X-ray: Note leveling of shoulders and improved symmetry of ribs and waist. (Figure 4)

The patient had a successful 2-stage procedure, undergoing first a nonsurgical decompression of the Chiari malformation followed by posterior spinal fusion with instrumention. Her main thoracic scoliosis curve was corrected to 34 degrees from preoperative magnitude of 84 degrees. Her lumbar compensatory curve improved from 46 degrees preoperatively to 21 degrees postoperatively (Figure 3). The asymmetry of her shoulders, waist and chest wall was dramatically improved. She remained free of any neurological symptoms.

References

  1. Diab M, Landman Z, Lubicky J, Dormans J, Erickson M, Richards BS, members of the Spinal Deformity Study Group. Use and outcome of MRI in the surgical treatment of adolescent idiopathic scoliosis. Spine, 36(8): 667-71, 2011 Apr 15.
  2. Zadeh H, Samir S, Powell M, Mehta M. Absent superficial abdominal reflexes in children with scoliosis: an early indicator of syringomyelia. J. Bone Joint Surgery (Br) 1995:77-B:767-2
  3. Wu L, Qui Y, Wang B, Zhu Z, Ma W. The left thoracic curve pattern: a strong predicator for neural axis abnormalities in patients with “idiopathic” scoliosis. Spine, 35; 2; 182-5, 2010.