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Title: Thoracic Insufficiency Syndrome

Authors: Oscar Mayer,MD, a Robert Campbell, MD, b Patrick Cahill,MD,b and Gregory Redding, MDc

Journal: CurrProblPediatrAdolesc Health Care. 46(3):72-97

Date: March 01, 2016

Excerpt: This article defines Thoracic Insufficiency Syndrome (TIS), explains how it is diagnosed and treated; helps to understand the treatment goals and the treatment results. It’s important to note, this paper is written from the viewpoint from one center and may not be the viewpoint of other doctors and experts. Parent Notes: A handful of parents with children with TIS reviewed this very detailed and comprehensive paper and found the information presented below to be the biggest takeaways.

Keywords: Early Onset Scoliosis, Growth Friendly Surgical, Thoracic Insufficiency, TIS, Pulmonary Function Testing

Summary:

What is Thoracic Insufficiency Syndrome?

TIS is a broad grouping of disorders that have a substantial impact on the chest wall, spine, and in many situations, both. Essentially, thoracic insufficiency syndrome (TIS) is the inability of the thorax to support normal breathing or lung growth. In normal developing children, lung growth parallels chest and spine growth. In children with thoracic insufficiency syndrome, lung growth is limited by rib deformities and spinal curves.

 

How is it diagnosed?

The diagnosis of TIS begins with a thorough medical history, physical examination and radiographs. In order to have a diagnosis of TIS a child must have a limitation of respiration or limitation of normal growth.

A diagnosis is made through physical examinations, Imaging Studies (x-rays, MRI, and/or CT scans) and Pulmonary Function Testing

How is it treated?

Surgery is considered when TIS has the potential to limit future lung growth or function. Growth-sparing spine and chest wall surgical strategies are most often used. These include: Vertical Expandable Prosthetic Titanium Rib (VEPTR), MAGEC Rods, Traditional Growth Rods, Short Segment Fusion are the common surgical intervention choices

What are the goals of treatment?

Treatment goals of progressive thoracic insufficiency syndrome are to increase in the thoracic volume while stabilizing and maintaining the chest-wall and spine. These improvements should continue as a patient grows.

How is success of treatment measured and defined?

It's important to note that surgical intervention can be a very effective and necessary treatment for TIS but it is not a cure. The ideal outcome for a patient is to see overall improvement in respiration, lung growth, and chest wall and spine distortion, however overall improvement is not the only indicator for success. For some patients, success is measured by the ability stabilize respiratory function or delay further respiratory decline. TIS is a complex condition which requires an individual treatment plan to not only achieve success after surgical intervention but to also define what success is for each individual.

 

TIS is a broad grouping of disorders

TIS occurs as a result of one of three underlining diseases:
  • Early-onset scoliosis, this includes various forms of early onset scoliosis and/or kyphosis often along with severe rib fusion and/or the congenital absence of ribs.
  • Primary thoracic dysplasia (short chest and rib cage or a narrow chest and rib cage) This includes Jeune syndrome and Jarcho-Levin syndrome
  • Neuromuscular dysfunction causing secondary spine and chest deformity. This includes various conditions such as spinal muscular atrophy, muscular dystrophies and static encephalopathy

 

Physical Examination:

  • Lips and fingertips are examined to for signs of cyanosis (bluish discoloration of the skin which can indicate poor circulation or inadequate blood oxygenation) Fingertips are also examined for clubbing (soft nail beds or nails that seem to 'float') these can be signs of long-term clinical hypoxemia (the body not getting enough oxygen)
  • Respiratory rates are measured and examined and compared to normal values
  • Chest Assessment - the chest is examined for clinical deformity and the circumference is measured and compared to normal values. A thumb excursion test is performed to measure the ability of each side of the chest to contribute respiration

Imaging Studies :

  • X-rays from the neck through the chest, abdomen and pelvis are necessary. Cobb angle of the spine's curves are measured, the height of the thoracic spine is measured.
  • CT scans of the entire chest and spine are sometimes needed. CT scan images provide a much clearer images and precise details and measurement of the chest and spine anatomy.
  • MRI of the entire spine and spinal cord are necessary to check for abnormalities to the spinal cord

 

Pulmonary Function Testing:

Pulmonary Function Testing (PFT) measure how well a child's lungs take in and release air and how well they move gases, such as oxygen, from the atmosphere into the body's circulation. These tests include spirometry, whole body plethysmography, single and multiple breath nitrogen washout, carbon monoxide diffusion capacity, respiratory muscle strength and lung compliance.

However, some of these tests are no possible in infants and toddlers simple because they cannot perform them on their own. Pulmonary lung function testing in children unable to perform the tests is done under anesthesia in the operating room. Lung function is measured passively with external pressure during inspiration and exhalation. This mechanical measurement has some caveats. It can underestimate early respiratory system dysfunction. However this still can produce helpful data.

Short Segment Spinal Fusion – is sometimes used to stabilize unstable portions of the spine. Total spinal fusion is generally no longer used in young children with TIS or EOS.

Growing Rods - Growing rods are surgical devices placed along your child's spine and attached to the spine with either hooks or screws above and below the curve. The area around the hooks and/or screws is fused to provide strong support. The curved part of the spine remains unfused.

  • Single growing rods are rarely used anymore. Single rods resulted in higher numbers of rod breakage, dislodgement , poor curve control and infections.
  • Dual growth rods are more successful. Studies have also shown best results have been obtained when lengthening operations are performed more frequently than biannually. Growing rods are FDA approved.

Vertical Expandable Prosthetic Titanium Rib (VEPTR) –The VEPTR attaches to the ribs and either the spine or hip bone. It helps correct spinal and chest deformity without fusing the spine. The VEPTR is typically lengthened every 6-12 months in the operating room. The VEPTR has more applicability than any other device because it can be used to support not only the spine but also the chest wall.

How the VEPTR is used on children with TIS has been subdivided into three categories:

  • Type I – the Absence of Ribs and Scoliosis – the thoracotomy is performed on the side that is missing ribs. The spine is then corrected through distraction which is stabilized by the VEPTR either rib-to-rib or rib-to-spine. Then chest wall stabilization is achieved by implanting an additional VEPTR rib-to-rib over the missing ribs.
  • Type II – Fused Ribs and Scoliosis – the thoracotomy is performed on side of the fused ribs. A crosswise surgical cut is performed for removal or separation of the fused rib is. VEPTR devices are added to the support the now open and expanded thorax and also along the spine to correct and stabilize both the spine and chest wall.
  • Type III – Hypoplasia of the Thorax – (a thorax that is too short or one that is too narrow)
    • Type IIIa(jarcho-levin syndrome or spondylothoracic dysplasia) A different approach is required here. A two-part surgical procedure is performed. A rib-to-rib VEPTR device is first inserted to lengthen or open and expand one side of the chest wall. The second is side is treated the same way approximately three months later with another surgical procedure.
    • Type IIIb(hypoplastic chest conditions, like Jeune syndrome) A different approach is required here as well. A VEPTR device is inserted on the right side in a unique manner with a side-to-side orientation in order to increase the overall thoracic size or volume. The second side is treated similarly approximately three months later.

MAGEC Rods – MAGEC rods are a specific type of growing rods. They are implanted in a similar manner to VEPTRs and growing rods. The unique feature of MAGEC rods are that they may be lengthened with the use of an external magnetic controller without the patient having to undergo an invasive procedure or even be placed under anesthesia. Lengthenings are performed in the doctor's office because the device does not require surgical lengthenings they are typically done more frequently as well.

Non-Surgical Approach of Serial Casting – Serial body casting is increasingly being utilized for the treatment of early onset scoliosis. In many cases casting can offer a way of straightening the spine over time. A cast is used to guide growth of the crooked spine into a straight spine. For some children, however, casting is used as a means to prevent or delay progression of scoliosis. This may be recommended to allow children to get bigger prior to surgery and also to increase lung development prior to surgery. Serial body casting can potentially play a major role in delaying or even eliminating the need for growth-sparing surgery with VEPTR or other growth rods but its ultimate effectiveness remains to be seen.