Blog Topic: Spinal Deformity in Neurofibromatosis Type 1

Surgical Case #2

7-20-2022

The next case is a 14 year old male with NF-1.  There are dystrophic changes to the spine around the thoracolumbar junction, specifically penciling of the ribs and scalloping of the vertebral bodies (red arrows).  This has induced a painful kyphoscoliosis.

The next pictures demonstrate there is some, but not much flexibility of the spine deformity.  The second picture from the left is a supine (laying on one’s back) radiograph.  The third from the left is a push-prone (laying on one’e stomach and radiology technicians pushing to try to improve the spine deformity. Neither of these two do much to change the spine deformity position.

The below two radiographs are performed with the patient actively bending to the left and right.

The below pictures are made from a CT scan, which is then rendered into a 3-dimensional picture which one can rotate around to better understand the deformity.  These particular images were made just prior to the creation of a 3-d model.

The below MRI images demonstrates dural ectasias (red arrows), vertebral scalloping (yellow arrows), and wedging of the vertebra (orange arrow).    The spinal cord (green arrow) is bent around the backside of the L1 vertebra.

The next pictures are intraoperative radiographs (x-rays).  Fixation of the spine can be very difficult (due to dural ectasias and vertebral scalloping) and the quality of the bone to be softer than normal (osteopenia).  Spinal deformity surgery of NF-1 patients requires preoperative CT and MRI evaluations to understand spines and where fixation could be placed and how to correct the spine deformity.  Surgery typically requires use of screws, hooks and sublaminar bands to successfully treat NF-1 spines.

After the L1 vertebra was completely (100%) removed a titanium cage (red arrow) was placed between the vertebra above (T12) and below (L2).  This cage increases the strength of the spine construct.

Below are the before and after surgery pictures.  The surgery nicely improves the spinal alignment on both views.  There was no weakness or sensory changes after surgery.  The patient’s preoperative pain resolved.

Multiple rods across the area where L1 was resected, and the cage was placed, to add more rigidity and durability.

 

Blog Topic: Spinal Deformity in Neurofibromatosis Type 1

Surgical Case

7-12-2022

The case presented is a 13 year old male with NF-1 who has a severe, progressive, painful kyphoscoliosis.

There is some inherent spinal flexibility as the thoracic kyphosis of 91 degrees improves when he lays on his back and hyperextends. 

The below selected MRI cuts demonstrates he does not have significant dural ectasias which could complicated surgery.  The axial MRI cut shows the spinal cord very eccentric in the canal, resting against the pedicle.  The spinal cord is slightly out-of-round, which elevates the risk of neurologic issues during surgery.

The below coronal CT scan cuts nicely shows the apex of the scoliosis having very abnormal vertebra.  Instead of being rectangular they are trapezoidal or triangular, which makes the scoliosis have a very tight turn.

The below axial CT scan cuts demonstrates the very abnormal pedicles.  Several of these pedicles (R T7, R T8 and R T9) are very difficult to place straight pedicle screws.  The reason these can be cannulated safely is due to the bone being malleable or bendable, and the pedicles can be bent straight (within reason).

The patients underwent 4 weeks of in-patient halo-gravity traction, with a maximum traction weight of 28 lbs. Despite the spine improving above and below the apex of the scoliosis, and the kyphosis improving, there still was a stiff apex.

Surgical treatment was a T3-L3 posterior spinal fusion and a T10 vertebral column resection, which means the entire T10 vertebra was removed.  This technique disconnects the spine and dramatically increases the flexibility of the spinal deformity.  After the spine was straightened a metal cage was placed in the front to help attain and maintain correction.

The patient is one year out from surgery and his doing well without pain.

 

 

Blog Topic: Spinal Deformity in Neurofibromatosis Type 1

7-10-2022

 

For details on Neurofibromatosis Type 1 (NF-1), I will refer you to Wikipedia:  https://en.wikipedia.org/wiki/Neurofibromatosis_type_I

As this blog focuses on spinal deformity in children and adolescents following is a brief summary as it relates to the musculoskeletal system (spine and extremities):

1.    1.  NF-1 causes tumors along nervous system which can grow anywhere on the body.

2.     2. Musculoskeletal abnormalities:

a.      Spine: Meningocoeles, dural ectasia, scoliosis, kyphosis

b.      Skeletal muscle weakness

c.      Long bones: pseudarthrosis (most commonly tibia), limb hypertrophy

3.      3. Approximately 20% of NF-1 patients will have spinal deformity.

4.     4. There are two types of spinal deformity in NF-1

a.      Idiopathic-like: looks and behaves more like idiopathic scoliosis

b.      Dystrophic

                                                    i.     Sharp, angulated spine deformity (kyphosis, scoliosis and kyphoscoliosis)

                                                   ii.     More common in the thoracic spine

                                                  iii.     Spines can start out having a more idiopathic-like deformity, which can change into a dystrophic type.

                                                  iv.     Causes penciling or thinning of the rib heads which can migrate into the spinal canal

 

 9 year old female

 

 

5.      5. Dural Ectasia: Circumferential enlargement or ballooning of the thecal sac, nerve root sleeves and spinal canal.

a.      More common in lumbar spine

b.      Causes vertebral body scalloping

c.      Also thins the pedicles

 

 

6.      6. Treatment

a.      For the idiopathic-like deformities, lower magnitude deformities are amenable to bracing. Surgical treatment mirrors guidelines for idiopathic scoliosis.

b.      For the dystrophic deformities:

                                                    i.     Bracing is limited in effectiveness

                                                   ii.     Surgery is performed for lower magnitude deformities due to the sharper-angulated deformities, increasing difficulty in achieving necessary spinal fixation and the risk of neurologic changes (such as weakness, sensory changes, bowel/bladder dysfunction).

Next several blog posts actual surgical cases of NF-1 will be presented.