Steven E. Kopits

Respiratory complications of achondroplasia

Nine patients with achondroplasia who were seen over a three-year period developed significant respiratory complications. Eight had sleep-disordered breathing, including obstructive sleep apnea in five, for which two required tracheostomy. Of the seven patients with significant hypoxemia, five had clinical evidence of cor pulmonale and recurrent pulmonary infiltrates. Two patients died, one with autopsy findings of compression of the medulla at the level of the foramen magnum and one with respiratory and cardiac failure. Appropriate therapy for our patients depended on recognition of the mechanisms that led to the respiratory complications, including (1) chest deformity, (2) upper airway obstruction and sleep-disordered breathing, (3) neurologic complications, and (4) coincidental chronic pulmonary conditions such as asthma.

Cervicomedullary compression in young patients with achondroplasia: Value of comprehensive neurologic and respiratory evaluation

We studied prospectively 26 young patients with achondroplasia to test two hypotheses: that respiratory problems may be the result of occult spinal cord compression, and that achondroplastic patients with cord compression might have occult respiratory abnormalities. Respiratory abnormalities were present in 85%, the majority caused by a primary problem of the pulmonary system, such as small thoracic cage or obstructed airway. Three patients had hypoxemia, recurrent cyanotic spells, and episodes of respiratory distress explainable only by cervicomedullary cord compression; in each patient, respiratory problems were alleviated by decompressive surgery. Another six patients with cervicomedullary compression had, in addition, at least one primary pulmonary cause of respiratory problems. After decompressive surgery the respiratory problems improved in three and were unchanged in three. Reconstructed sagittal CT images proved the most sensitive technique for detecting craniocervical stenosis as a cause of cervicomedullary cord compression, although some degree of stenosis was present in nearly all of the patients.

Thoracolumbar Kyphosis and Lumbosacral Hyperlordosis in Achondroplastic Children

The thoracolumbar (TL) kyphosis is present at birth, or is noticed within the first 6 months in about 95% of newborns. The curve becomes more pronounced and gains its maximal expression when the child becomes a sitter, between 6 and 18 months of age (Fig. la,b). It noticeably improves or even disappears in most children with the advent of stance and gait, simultaneously with the development of lumbosacral lordosis. Some infants, however, develop vertebral wedging of the apical vertebra that insures the permanence of a residual structural curve. Many other achondroplasts adopt a kyphotic posture while sitting throughout life even if they do not have a structural, clinically appearing kyphosis when standing.

Reconstructive Surgery in Children with Azotemic Osteodystrophy

Current techniques of medical management have extended the lives of many uremie children. Five patients with azotemic osteodystrophy are reported, four of whom underwent successful reconstructive orthopaedic surgery. The selection of patients with azotemic osteodystrophy for surgery includes considerations of life expectancy, effectiveness of medical management in controlling the metabolic bone disease, surgical risk, and the amenability of the orthopaedic disorder to definitive surgical procedures. Successful operative management of these patients requires careful and close medical supervision by physicians skilled in the treatment of uremia. The management of some specific paraoperative problems requires the close cooperation of surgeon, anesthetist, and pediatrician. Bone healing time was normal in these patients.

Total Craniospinal Decompression in Achondroplastic Stenosis

We describe our experience with total craniospinal decompression along the entire neuraxis, extending from the brain stem to the cauda equina, in seven patients with achondroplasia. These patients presented with clinically significant compression at multiple levels. In these patients, there were focal areas of complete myelographic block, typically at the cervicothoracic or thoracolumbar junction, as well as diffuse narrowing of the entire spinal subarachnoid space. In some, there were further complications of basilar impression, Arnold-Chiari malformation, or syringomyelia. Total craniospinal decompression was completed in either one or two stages. Only a small minority of our patients with achondroplasia had critical stenosis over this many levels, requiring total craniospinal decompression. However, with proper preparation and technique, we found that patients can tolerate even such an extensive decompressive procedure and benefit from surgery without suffering postoperative spinal instability.

Orthopedic Aspects of Achondroplasia in Children

The majority of achondroplastic children are fit and able throughout their early childhood. A small minority are disabled by cervico-medullary compression at the foramen magnum or by chronic recurrent otitis media. The first complaints in neurologically intact children are of leg pain due to progressive deformity at about 6 years of age.

Surgical Management of Cervicomedullary Compression in Achondroplastic Patients

In this segment it will not be necessary to go over the clinical presentations and pre-operative evaluations that are an essential part of the management of achondroplastic patients. It is sufficient to say that the clinical presentations such as delayed motor milestones, hyperreflexia and clonus, multiparesis, respiratory insufficiency and/or apnea, and obstructive sleep apnea are sufficient enough to warrant investigations to exclude cervicomedullary compression. If present, the evidence already presented during this conference in terms of outcome would justify surgical intervention. We will concentrate on the surgical preparation and the actual surgical procedure for decompressing the cervicomedullary region.

Extended Laminectomy for Spinal Stenosis in Achondroplasia

Achondroplasia is the most common chondrodysplasia, an autosomal dominant condition with an incidence of 17–29 per million (1). The basic defect is in endochondral bone formation, the cause of which is unknown (2). The abnormal bone growth leads to the typical skeletal features of rhizomelic limb shortening, frontal bossing, lumbar lordosis and narrowing of the spinal canal. Neurological complications have been attributed to the skeletal abnormalities since the early 1900’s, when the narrowed lumbar canal was recognized as a cause of paraplegia (3). In 1925, Donath and Vogl (4) provided the first detailed description of the structural changes in the vertebral column resulting in neurological complications. Their autopsy studies revealed a decrease in size of the thoracic spinal canal in achondroplasts due to shortened vertebral bodies and pedicles. Later studies have demonstrated a reduction in size of the entire spinal canal (5), with caudal tapering (6) and stenosis of nerve root canals (7). The spinal cord and cauda equina are normal in size (6,8). In addition, the intervertebral discs are congenitally hyperplastic and tend to bulge laterally and posteriorly (6).

The Subarachnoid Fluid Space in Achondroplastic Spinal Stenosis: The Surgical Implication

The tragic outcome of decompressive laminectomy in patients with achondroplastic spinal stenosis has been reported (1, 2, 3, 4). Our experience at the Johns Hopkins Medical Institutions supports the observations in the literature. The poor outcome is caused mainly by the extremely stenotic canal, which makes adequate decompression difficult (5, 6, 7, 8, 9, 10, 11). Furthermore, the degree and extent of the spinal stenosis were frequently not clearly delineated by conventional myelography. However, intrathecal enhanced CT provides not only superb bony detail but also delineation of the soft-tissue content of the spinal canal (12). The relationships between the spinal cord and its surrounding subarachnoid space are also well demonstrated. This paper reports the depth of the subarachnoid fluid space surrounding the spinal cord at the cervical and thoracic levels, measured from the intrathecal enhanced axial CT images of 11 adult achondroplastic patients. It describes a modified decompressive laminectomy technique devised by the authors (S.U.) that has been applied in over 20 cases of achondroplastic spinal stenosis. It has helped to prevent the infliction of undue trauma on the neural tissue during the surgical manoeuvers.