Neurologic abnormalities in the skeletal dysplasias: a clinical and radiological perspective

A patient with pycnodysostosis presenting with seizures and porencephalic cysts

Pycnodysostosis is a rare autosomal recessive disorder caused by mutations in the cysteine protease Cathepsin K gene located on chromosome 1q21. It has a well characterized skeletal phenotype which include short stature, generalized increased bone density with propensity of fractures, open calvarial sutures and fontanelle, dental abnormalities, obtuse mandibular angle, resorption of lateral end of clavicle, acro-osteolysis, and in some cases visceromegaly. Central nervous system involvement is very rare and porencephalic cysts has been reported only once, the cause being hypothesised to be an imbalance between the growing brain, its vascular supply and intraventricular fluid pressure. We had a patient with bilateral frontal lobe porencephalic cysts; the patient presenting with complex partial seizures. Cathepsins have been found to be involved in neurological diseases and role of proteases has been well established in gliosis.

Progression of low back and lower extremity pain in a cohort of patients with achondroplasia

OBJECT

The aim of this study was to assess the natural history of pain associated with spinal stenosis in individuals with achondroplasia and to characterize pain patterns and associated functional and psychological effects.

METHODS

The authors measured pain severity, spatial distribution of pain, functional disability, psychological distress, physical symptoms other than pain, and healthcare utilization in 181 individuals with achondroplasia. They also assessed low back and/or lower extremity pain at the initial visit and 1-year follow-up via self-rated patient questionnaires, calculated composite scores from responses via component analyses, and used repeated measures linear regression analyses for score changes (significance, p < or = 0.05).

RESULTS

At the follow-up, back pain severity was unchanged. Patients reported significant progression of pain toward involvement of the lower extremities and significant increases in lower extremity pain severity overall. There were also significant increases in healthcare utilization overall. Compared with patients with back pain only, those with back pain and proximal or distal leg pain had higher self-rated pain severity; higher functional disability; and more bowel and bladder dysfunction symptoms, sleep disturbances, extremity numbness, and psychological distress.

CONCLUSIONS

Individuals with achondroplasia and symptomatic spinal stenosis often experience back pain, which may progress to lower extremity pain and debilitating consequences. A more thorough understanding of the progression of spatial pain characteristics and pain severity may aid clinical decision making regarding the optimal timing for intervention.

Achondroplasia

Achondroplasia is the most common form of short limb dwarfism in human beings, affecting more than 250,000 individuals worldwide. More than 95% of patients have the same point mutation in the gene for fibroblast growth factor receptor 3 (FGFR3) and more than 80% of these are new mutations. The mutation, which causes gain of FGFR3 function, affects many tissues, most strikingly the cartilaginous growth plate in the growing skeleton, leading to a variety of manifestations and complications. The biology of FGFR3 and the molecular and cellular consequences of the achondroplasia mutation are being elucidated, providing a more complete understanding of the disorder and a basis for future treatments targeted directly at relevant pathogenetic pathways. Furthermore, the natural history of the condition, which has been well delineated in childhood and adolescence, is being defined more fully in adults with achondroplasia; most of the serious complications can be modified favourably or prevented by anticipation and early treatment. Possible future treatments include chemical inhibition of receptor signalling, antibody blockade of receptor activation, and alteration of pathways that modulate the downstream propagation of FGFR3 signals.

When is enlargement of the subarachnoid spaces not benign? A genetic perspective

Enlargement of the subarachnoid spaces is occasionally encountered during neuroimaging of children. This enlargement is generally regarded as a nonpathologic process that resolves uneventfully. However, there are several genetic disorders in which enlargement of the subarachnoid spaces can be an early sign, or the feature of an associated syndrome, that may aid in the underlying diagnosis. Recognizing subarachnoid space enlargement in these circumstances requires an understanding of the normal physiology of the subarachnoid space at different time points in a child's neurodevelopment. This article reviews the events shaping the subarachnoid space, both during normal physiologic maturation and in specific genetic disorders.

Advances in understanding etiology of achondroplasia and review of management

PURPOSE OF REVIEW

A summary of management and current research in achondroplasia (OMIM 100800). The most common nonlethal skeletal dysplasia, achondroplasia presents a distinct clinical picture evident at birth. Substantial information is available concerning the natural history of this dwarfing disorder. Diagnosis is made by clinical findings and radiographic features. Characteristic features include short limbs, a relatively large head with frontal bossing and midface hypoplasia, trident hands, muscular hypotonia, and thoracolumbar kyphosis. Children commonly have recurrent ear infections, delayed motor milestones, and eventually develop bowed legs and lumbar lordosis. People with achondroplasia are generally of normal intelligence.

RECENT FINDINGS

The genetic cause of achondroplasia was discovered in 1994. Subsequent research efforts are designed to better characterize the underlying possible biochemical mechanisms responsible for the clinical findings of achondroplasia as well as to develop possible new therapies and/or improve intervention.

SUMMARY

Establishing a diagnosis of achondroplasia allows families and clinicians to provide anticipatory care for affected children. Although the primary features of achondroplasia affect the skeleton, a multidisciplinary approach to care for children with achondroplasia helps families and clinicians understand the clinical findings and the natural history of achondroplasia in order to improve the outcome for each patient.

Severe neurological complications in skeletal dysplasias: two case reports

Skeletal dysplasias form a diverse and genetically heterogeneous group of disorders, but also share many clinical and radiographic features. We describe two illustrative cases and provide a short review of the literature on the neurological complications associated with various groups of skeletal dysplasias. These two cases illustrate that management of skeletal dysplasias requires a multidisciplinary approach, aimed at preventing or minimizing medical complications. Follow-up should include regular comprehensive neurological evaluation, as neurological complications can be severe and are often treatable if diagnosed at an early stage.

"The disappearing evoked potentials": a special problem of positioning patients with skeletal dysplasia: case report

STUDY DESIGN

A retrospective study of 3 patients with skeletal dysplasia, who had a loss of the evoked potentials during prone positioning before spine surgical intervention.

OBJECTIVES

To bring attention to the potential hazard of neurologic compromise during the positioning of patients with skeletal dysplasia for spine surgery. Recommendations are suggested to prevent the disappearance of intraoperative evoked potentials and, therefore, possible neural injury in these patients.

SUMMARY OF BACKGROUND DATA

In a very few published cases, loss or attenuation of monitored potentials has been observed at the time of initial patient positioning. Although patients with skeletal dysplasia might be considered particularly vulnerable to spinal cord injury caused by malpositioning of the head and neck, to our knowledge, no association with lost evoked potentials has previously been described.

METHODS

Intraoperative transcranial electrical motor-evoked potential and/or somatosensory evoked potential baseline studies were performed after induction in the supine position. These studies were repeated as soon as practicable, after intubation and, again, after the patients were turned prone. The neurophysiologist informed the surgeon that evoked potential change in latency or amplitude met warning criteria. Alteration in the surgical plan resulted in successful spinal surgery in these cases.

RESULTS

In case No. 1, repositioning of the head in flexion was sufficient to return the evoked potentials to normal. In the other two cases, attempts to reposition the patients prone failed, and the procedures were abandoned. In case No. 2, four months after the initial surgery, a halo cast for immobilization and craniocervical decompression were needed before the corrective cervical spine surgery, and in case No. 3, two steps were taken after the initial surgery: 1) trial positioning awake on the surgical table before surgery; and 2) awake postintubation prone positioning on the actual surgery day.

CONCLUSIONS

Patients with skeletal dysplasia are susceptible to serious neurologic misadventure when turned to a prone position. Neurophysiologic and/or clinical monitoring of patient positioning should be undertaken, and a plan of intervention, should loss of signal or function occur, must be implemented.

Congenital abnormalities of the musculoskeletal system: Perinatal evaluation and long-term outcome

Many musculoskeletal malformations can be detected by prenatal US. Whether isolated or part of a syndrome, these anomalies can have a significant impact on the entire life of the individual. Nonfatal conditions may be subtle and become more recognizable in the second and third trimester. After delivery, radiography helps confirm the diagnosis. US, CT, and MRI all have a role in imaging the primary abnormality, the follow-up effects of treatment, and in monitoring for potential complications that may develop over time. Three-dimensional imaging has an increasing role, in US, CT, and MRI, both in the prenatal and postnatal periods.

Patient with the mesomelic dysplasia, Nievergelt syndrome, and cerebellovermian agenesis and cataracts

We describe a 33-day-old boy who had short and thick tibiae, symmetrical oligosyndactyly of the hands, and distinctive face. The patient was considered as a case of Nievergelt syndrome, a rare form of mesomelic dysplasia. Besides the characteristic mesomelic limb anomalies of Nievergelt syndrome, this patient exhibited two additional features: agenesis of the cerebellar vermis and cataracts, both of which have not been previously reported.

Skeletal dysplasias and their effect on the respiratory system

Children with skeletal dysplasia frequently have pulmonary disease which can be life threatening. These pulmonary problems are due to multiple aetiologies including thoracic and craniofacial anomalies predisposing to restrictive lung disease, upper airway obstruction and central apnoea. Recognition of pulmonary disease and early intervention improves the survival and quality of life for these children.

Cranioectodermal dysplasia: a new patient with an inapparent, subtle phenotype

Cranioectodermal dysplasia is a rare syndrome characterized by craniofacial and skeletal anomalies and ectodermal dysplasia. Life-threatening associated conditions (i.e., kidney failure and abnormal regulation of the parathyroid-bone axis) can also develop. We report a patient whose features are suggestive of an inapparent, subtle phenotype of the syndrome. The patient is a 4-year-old girl with only dolichocephaly and clinodactyly; microdontia, hypodontia, and taurodontia (i.e., cone-shaped teeth); anteverted nares, full cheeks, and everted lower lip; epicanthal folds, hypertelorism and hyperopia; and corpus callosum hypoplasia. She has no rhizomelic limb shortening or hair abnormalities. In view of the rarity of the cranioectodermal dysplasias, the variability of the phenotype, and the uncertain outcome of some previously described patients, we believe this inapparent, subtle case should reported to enable better understanding and treatment of this rare syndrome.

Isolated subaxial cervical spine stenosis in achondroplasia

Although isolated subaxial cervical spine stenosis in achondroplasia is less common than narrowing at the foramen magnum, thoracolumbar junction, or lumbar spine, it should be recognized as a distinct entity. These congenital changes usually become symptomatic when combined with degenerative changes in early adult life. Yearly monitoring of adult achondroplastic patients for signs and symptoms of cervical myelopathy or radiculopathy is recommended. When this develops, early surgical decompression should be considered, as these patients generally do not respond well to nonoperative treatment. The altered anatomy and small size make these cases particularly challenging. A thorough history and examination and complete diagnostic testing are necessary to gain an understanding of the exact etiology of the symptoms. Wide laminectomies and foraminotomies are then usually required to decompress the spinal cord and nerve roots. Fusion using internal fixation may be required to stabilize the spine if excessive bone is removed. (Curr Surg 57:354-356)