Dynamic cervicomedullary cord compression and alterations in cerebrospinal fluid dynamics in children with achondroplasia: review of an 11-year surgical case series

Clinical article

Full access

Object

Achondroplasia may be associated with compression at the cervicomedullary junction. Determining which patients are at greatest risk for neurological complications of cervicomedullary compression can be difficult. In the current study the authors reviewed their records to determine the incidence and clinical significance of dynamic cervicomedullary stenosis and obstruction of CSF flow along with surgical outcomes following posterior fossa decompression.

Methods

The authors reviewed 34 consecutive cases involving symptomatic children with achondroplasia undergoing cervicomedullary decompression performed by a single surgeon over 11 years. Of these patients, 29 had undergone preoperative dynamic MRI of the cervicomedullary junction with cine (cinema) CSF flow studies; 13 of these patients underwent postoperative dynamic MRI studies. Clinical outcomes included changes in polysomnography, head circumference percentile, and fontanel characteristics. Radiographic outcomes included changes in dynamic spinal cord diameter, improvement in CSF flow at the foramen magnum, and change in the Evans ratio.

Results

Patients were predominantly female, with a mean age at presentation of 6.6 years and mean follow-up of 3.7 years (range 1–10 years).

All patients had moderate to excellent improvement in postoperative polysomnography, slight decrease in average head circumference percentile (from 46.9th percentile to 45.7th percentile), and no subjective worsening of fontanel characteristics. The Evans ratio decreased by 2%, spinal cord diameter increased an average of 3.1 mm, 5.2 mm, and 0.2 mm in the neutral, flexed, and extended positions, respectively, and CSF flow improved qualitatively in all 3 positions. There were no postoperative infections, CSF leaks, or other major complications. None of the patients undergoing initial foramen magnum decompression performed at our medical center required reoperation.

Conclusions

Patients with achondroplasia and symptomatic cervicomedullary compression have increased risk of dynamic stenosis at the foramen magnum evident upon dynamic cine MRI. Operative decompression may be offered with low risk of complications or need for reoperation.

Abbreviations used in this paper:CMJ = cervicomedullary junction; VP = ventriculoperitoneal.

Abstract

Object

Achondroplasia may be associated with compression at the cervicomedullary junction. Determining which patients are at greatest risk for neurological complications of cervicomedullary compression can be difficult. In the current study the authors reviewed their records to determine the incidence and clinical significance of dynamic cervicomedullary stenosis and obstruction of CSF flow along with surgical outcomes following posterior fossa decompression.

Methods

The authors reviewed 34 consecutive cases involving symptomatic children with achondroplasia undergoing cervicomedullary decompression performed by a single surgeon over 11 years. Of these patients, 29 had undergone preoperative dynamic MRI of the cervicomedullary junction with cine (cinema) CSF flow studies; 13 of these patients underwent postoperative dynamic MRI studies. Clinical outcomes included changes in polysomnography, head circumference percentile, and fontanel characteristics. Radiographic outcomes included changes in dynamic spinal cord diameter, improvement in CSF flow at the foramen magnum, and change in the Evans ratio.

Results

Patients were predominantly female, with a mean age at presentation of 6.6 years and mean follow-up of 3.7 years (range 1–10 years).

All patients had moderate to excellent improvement in postoperative polysomnography, slight decrease in average head circumference percentile (from 46.9th percentile to 45.7th percentile), and no subjective worsening of fontanel characteristics. The Evans ratio decreased by 2%, spinal cord diameter increased an average of 3.1 mm, 5.2 mm, and 0.2 mm in the neutral, flexed, and extended positions, respectively, and CSF flow improved qualitatively in all 3 positions. There were no postoperative infections, CSF leaks, or other major complications. None of the patients undergoing initial foramen magnum decompression performed at our medical center required reoperation.

Conclusions

Patients with achondroplasia and symptomatic cervicomedullary compression have increased risk of dynamic stenosis at the foramen magnum evident upon dynamic cine MRI. Operative decompression may be offered with low risk of complications or need for reoperation.

Achondroplasia is the most common of the skeletal dysplasias.21 It is an autosomal dominant condition, with most cases due to new activating mutations in the FGFR3 gene. The molecular defect in achondroplasia causes a quantitative decrease in the rate of endochondral bone formation, resulting in short and wide long bones, short stature, a large calvaria, midface hypoplasia, and a short basicranium with narrowed foramen magnum and vascular channels (Fig. 1).10,17,21

Fig. 1.
Fig. 1.

Activating mutations in FGFR3 within chondrocytes can lead to spinal stenosis, central sleep apnea, or hydrocephalus by decreasing the relative rate of endochondral bone formation.

The most serious neurological complication in patients with achondroplasia is cervicomedullary junction (CMJ) compression caused by a tight deformed foramen magnum.10,13 Compression at the foramen magnum can result in cervical myelopathy manifested as clonus and hyperreflexia, hypotonia, sleep apnea, and even sudden death.2,3,8,10,17 Due to the potentially lethal complications associated with symptomatic disease, neurosurgical decompression has been used to widen the foramen magnum and relieve the pressure on the emerging cervical cord. Fortunately, most children with achondroplasia do not suffer neurological symptoms and achieve normal motor and intellectual development without surgical intervention.8,12,19

Criteria for decompression have been previously described in large surgical series.17,20 Unfortunately, there has never been a study that provided a fail-safe method for prospectively identifying patients who are likely to die or experience severe neurological complications if decompression surgery was not performed. This left clinicians with the possibility of performing operations on individuals who would have spontaneously gained normal neurological function with time.

Past surgical series have focused on the surgical treatment of static myelopathy attributed to fixed cervicomedullary compression at the level of the foramen magnum.2,3,10,19,20 We previously identified 4 infants and children with achondroplasia who developed symptoms of cervicomedullary compression with their necks in flexed position. In 3 of these children, we demonstrated significantly diminished or blocked CSF flow anterior to the spinal cord with the neck in flexed position.6 It remained unclear 1) what percentage of symptomatic patients have a normal MRI scan in neutral position but have significant cervicomedullary compression and obstruction of flow on dynamic studies, 2) whether patients undergoing a bony foramen magnum decompression without placement of a patch graft have an adequate decompression which establishes CSF flow, and, finally, 3) whether there is a group of patients who are minimally symptomatic but have a higher risk of progression that can be predicted based on dynamic studies. We attempted to gain some insight into these questions with an 11-year retrospective review of a single-institution, single-surgeon surgical series of 35 symptomatic patients with achondroplasia, a large proportion whom were evaluated for cervicomedullary compression using dynamic cervical flexion/extension MRI and CSF flow studies, and underwent cervicomedullary decompression.

Methods

All patients with achondroplasia and symptomatic foramen magnum stenosis who were referred for neurosurgical evaluation between the years 2000 and 2010 at Cedars-Sinai Medical Center and subsequently underwent cervicomedullary decompression were identified.

Presenting signs/symptoms including sleep apnea, nausea, vomiting, incontinence, headaches, full fontanel, clonus, excessive sweating, dilated facial veins, hyperreflexia, abnormal tone, gait disturbance, paresthesias of the extremities, weakness, hyperreflexia, or other signs of myelopathy were documented. Additionally, head circumference was measured on all presenting patients and documented on an achondroplasia head circumference growth chart. Criteria for symptomatic patients with cervicomedullary compression to undergo decompression were based on previously published clinical and radiographic measures.6

All patients underwent preoperative and postoperative polysomnography studies as well as MRI of the brain and cervical spine. On brain imaging, a ventricular ratio was calculated for all patients to assist in cataloging the extent of ventriculomegaly Additionally, 29 of the 34 patients underwent preoperative dynamic imaging studies (T1-weighted, T2-weighted, cine MRI) of the cervical spine in neutral, flexion, and extension positions. Thirteen of these 29 patients had postoperative dynamic MRI studies performed between 1 and 3 months following decompression. Primary measurements in these positions included the narrowest portion of the CMJ, the spinal cord diameter at the CMJ, C1–2 anterior ligamentous complex thickness, and the diameter of the foramen magnum (Figs. 24).

Fig. 2.
Fig. 2.

Primary measurements made using sagittal MR images of the cervical spine in neutral (A and B) and flexed (C) positions included the narrowest portion of the cervical spinal canal (green line), the spinal cord diameter at the cervicomedullary junction (red line), and thickness of the anterior ligamentous complex (blue line). These measurements regularly changed in the flexed versus neutral positions.

Fig. 3.
Fig. 3.

Dynamic T2-weighted (A and C) and cine (B and D) sagittal MR images of the cervical spine demonstrating cervical stenosis greater in flexion (A and B) than in extension (C and D).

Fig. 4.
Fig. 4.

Preoperative (A and B) and postoperative (C and D) T2- weighted (A and C) and cine (B and D) sagittal MR images obtained in a single patient in the neutral position illustrating decompression (C) and improved flow (D) postoperatively.

Head circumference centiles were determined using a standardized head circumference chart for patients with achondroplasia. Additionally, the Evans ratio, as defined in the axial plane as the ratio of the diameter of the largest bifrontal measure of the ventricles over the corresponding bifrontal measure of the intracranial cavity, was documented and used as a way to compare ventricles over time within the same patient. Although an Evans ratio of at least 0.3 is consistent with a diagnosis of hydrocephalus in patients of average height, this ratio has not been directly validated in the population of patients with achondroplasia and was not used in our patients to assess for the presence or absence of hydrocephalus (Fig. 5).

Fig. 5.
Fig. 5.

The Evans ratio is defined as the maximum ventricular width (red line) divided by the largest biparietal distance between the inner tables of the skull (green line). An Evans ratio of at least 0.3 may be consistent with a diagnosis of hydrocephalus.

Postoperative primary outcome measurements included clinical results of postoperative polysomnography studies, changes in presenting signs and/or symptoms, and radiographic outcomes, such as change in ventricular size, presence or absence of CSF flow, and the diameter of the spinal cord in neutral, flexion, and extension.

The Pearson chi-square test was used to assess bivariate outcomes between radiographic changes in spinal cord diameter and clinical outcomes such as a full fontanel.

Surgical Technique

All patients diagnosed with symptomatic cervicomedullary compression and foramen magnum stenosis underwent foramen magnum decompression and removal of the posterior ring of C-1. Suboccipital craniectomy for decompression of the foramen magnum has been previously reported.1,4 We used a modified procedure whereby the dura was not opened surgically.

Following induction of general anesthesia and placement of appropriate lines, the patients were positioned prone on the operating room table with the head and neck supported in a pediatric horseshoe in slight flexion. Upper-extremity and lower-extremity somatosensory evoked potentials were routinely assessed before and after positioning as well as throughout the surgical procedure. A midline suboccipital incision was marked and indurated with local anesthetic followed by an incision from the inion down to the spinous process of C-2. Incision was extended in the midline plane down to the suboccipital area and lamina of C-1. A subperiosteal dissection was performed to expose the occiput and the posterior ring of C-1. The operating microscope was then brought into the field, and a high-speed drill and curettes were used to remove the posterior ring of C-1. To ensure an adequate lateral decompression, care was taken to extend the craniectomy out laterally and anteriorly to the point where the dura of the cervicomedullary junction would curve anteriorly. As has previously been described,1 the posterior rim of the foramen magnum was thickened and in many cases was found to curve in the cephalad direction. To minimize the risk of a dural tear, we first would thin out the suboccipital bone to a thin shelf posterior to the rim of the foramen magnum while leaving the lip of foramen magnum intact. We would then continue to use a highspeed drill, microcurettes, and 1-mm Kerrison rongeurs to resect the remaining posterior ring of the foramen magnum. An abnormally thick fibrous ligamentous band was frequently encountered; it was incised without opening the dura itself. The outer leaf of the dura was then scored with a No. 15 scalpel as needed to allow for better expansion of the dura. Ultrasound was frequently used to confirm adequate decompression in addition to observing improved dural pulsations. The wound was irrigated with antibiotic solution and then closed in multilayer anatomical fashion. Most of the patients were extubated at the end of the operation and sent to the pediatric intensive care unit. Extubation was delayed in patients with either a history of severe obstructive sleep apnea or the presence of facial and laryngeal edema.

Results

Overall Cohort

A total of 34 patients were identified who presented with symptomatic foramen magnum stenosis and underwent cervicomedullary decompression (Table 1) based on previously described criteria.6 Their mean age at presentation was 6.6 years old, and there was a slight female predominance (23 female patients). The mean duration of follow-up was 3.7 years (range 1–10 years). Among all patients, spinal cord diameter increased by 5.2 mm on postoperative MRI of the cervical spine in neutral position.

TABLE 1:

Presenting signs and symptoms in the 34 patients with achondroplasia and symptomatic foramen magnum stenosis who underwent cervicomedullary decompression

Presenting Signs and SymptomsNo. of Patients
symptoms
 sleep apnea34
 hydrocephalus8
 nausea/emesis8
 incontinence5
 myelopathy4
 headaches3
signs
 full fontanel20
 abnormal tone18
 clonus14
 excessive sweating12
 dilated facial veins11
 weakness8
 hyperreflexia8
 gait disturbance5
 numbness4

Subset With Flexion-Extension Imaging

A total of 29 of the 34 patients had preoperative flexion-extension dynamic MRI cine flow studies, with 13 of these patients having postoperative follow-up dynamic MRI cine flow studies as well. All 29 patients were found to have central sleep apnea at presentation, while 5 patients were hydrocephalic, 5 had a history of nausea/emesis, 4 were incontinent, and 2 presented with headaches. Additionally, 18 presented with a full fontanel, 17 with abnormal tone, 12 with clonus, 10 with excessive sweating, 11 with dilated facial veins, 6 with paresis, 6 with hyperreflexia, 3 with gait disturbance, and 2 with paresthesias in the extremities.

Preoperatively, the average change in spinal cord diameter from extension to flexion was −1.9 mm (range −0.7 to −3.9 mm). Preoperatively, the average change in spinal cord diameter from neutral to flexion was −1.7 mm (range−0.2 to −2.9 mm). Postoperatively, the average change in spinal cord diameter from extension to flexion was −4.2 mm (range −1.7 to −5.2 mm). Postoperatively, the average change in spinal cord diameter from neutral to flexion was −3.2 mm (range −1.8 to −4.2 mm). Relative to preoperative values, the average increase in spinal cord diameter postoperatively was +3.1 mm in neutral position, +5.4 mm in flexion position, and +0.2 mm in extension position. The ventricular ratio remained relatively unchanged, from a value of 0.37 preoperatively to 0.33 postoperatively. Postoperative cine MRI studies demonstrated improved CSF flow in in all patients (13 of 13 patients).

Four of the 29 patients with flexion-extension imaging had significant stenosis on flexion imaging without obliteration of CSF flow anterior to the cord on neutral images. This was equal to 13.7% of symptomatic achondroplastic patients in whom spinal cord compression with obliteration of CSF flow anterior to the cord was only evident on flexion-extension imaging, and not with the neck in neutral position.

Postoperative polysomnography demonstrated moderate to complete resolution of central sleep apnea in all patients. None of our patients required red blood cell transfusions intraoperatively or perioperatively. Head circumference remained relatively unchanged from a mean preoperative head circumference in the 46.9th centile to a postoperative head circumference in the 45.7th centile, using the achondroplasia head circumference centile chart. Eighteen patients presented with a full fontanel, with none worsening in the postoperative period. None of these patients demonstrated any increase in head circumference centile postoperatively over time, despite several having accelerated head circumference growth or a full fontanel preoperatively. One patient in the series required a ventriculoperitoneal (VP) shunt for hydrocephalus, although the VP shunt procedure predated the cervicomedullary decompression operation.

Discussion

The existing literature has focused on the surgical treatment and outcomes of fixed cervicomedullary compression due to foramen magnum stenosis.2,8,10,19,21 Unfortunately, there continues to be controversy over the degree of risk for sudden death in children with achondroplasia, how often to operate, the indications for decompression, and surgical methods that should be used. Criteria for decompression in large surgical series17 have not provided a fail-safe method for prospectively identifying patients who are likely to die or experience severe neurological complications without surgical decompression. Additionally, there appears to be a group of patients who can be symptomatic, with signs of elevated intracranial pressure or compression of the cervicomedullary junction due to dynamic phenomenon.6 Unfortunately, this may result in surgeries undertaken in individuals who would have spontaneously gained normal neurological function with time or in needed surgery being withheld from patients with normal imaging findings of the cervical spine in neutral position.

At our center, we follow infants with achondroplasia using MRI that incorporates CSF flow studies with the cervical spine in neutral, flexed, and extended positions. Most infants with achondroplasia have a decreased amount of space around the emerging cervical cord, and frequently the lip of the foramen magnum indents the posterior spinal cord. As these children grow older and gain normal motor development, the impingement on the cord decreases and may eventually disappear, presumably because the size of the foramen magnum is growing faster than the size of the spinal cord. In fact, the changes present in the spinal cord and the indentation or the emerging cord may persist despite normal neurological function. We have used complete obliteration of CSF flow anterior to the spinal cord as an indication for decompression in symptomatic patients.

Previously at our center we identified 4 otherwise healthy infants and children with achondroplasia who developed symptoms of cervicomedullary compression with their necks in flexed position. In 3 of these children, we found evidence of adequate CSF flow at the foramen magnum when the MR images were taken at a neutral position, but dramatically diminished or completely blocked CSF flow when the neck was flexed. These 3 symptomatic patients would not have undergone a decompression procedure without the benefit of flexion-extension studies demonstrating cervicomedullary compression and obstruction of CSF flow with the cervical spine in the flexed position. All 3 of these patients had dramatic improvement in central sleep apnea and headaches after undergoing a decompression procedure. We therefore decided to review an 11-year single surgeon surgical experience in our institution to determine the incidence of dynamic cervicomedullary compression that is only demonstrable with the cervical spine in the flexed position.

In the current review of our surgical series, we found that 14% of our symptomatic patients who underwent a dynamic preoperative flexion and extension CSF flow study would not have otherwise been candidates for decompression procedures. In other words, 14% of the patients who underwent foramen magnum decompression met our criteria for decompression based on obliteration of CSF flow anterior to the CMJ on MRI studies of the cervical spine in a flexed position. While the majority of patients undergoing a decompression procedure had significant stenosis on neutral studies that was worse on flexion, these patients did not have significant constriction of the spinal cord in neutral position that would have led us to recommend a cervicomedullary decompression.

Additionally, many patients with preoperative central sleep apnea do not have complete resolution but do have significant improvement of their sleep studies. In assessing the adequacy of decompression procedure in this subgroup of patients, we found postoperative dynamic studies to be very helpful, as they were the most effective in demonstrating any significant residual or recurrent compression.

One unexpected observation in our study regarded the improvement in the fullness of the anterior fontanel and the apparent lack of progressive ventriculomegaly or jump in head circumference centiles in any of the patients who underwent a foramen magnum decompression. Our observation is very difficult to interpret as ventriculomegaly is well documented in achondroplasia,5,7,9,15,16,18,22 but the clinical significance of ventriculomegaly and definition of hydrocephalus can be elusive and controversial. In fact, standardized head circumference centile charts for children with achondroplasia were created without measurements of the size of the ventricles or measurements of intracranial pressures.11 Steinbok et al.22 pointed out that the enlarged head circumferences in patients with achondroplasia may in fact “reflect a significant incidence of underlying hydrocephalus in achondroplastic patients.” In their study they monitored intraventricular pressure followed by injection of radionucleotides in 5 children with achondroplasia. The intraventricular pressure was elevated and the reabsorption of CSF into the sagittal sinus was slow in all cases, but there was no demonstrable obstruction to CSF flow. Jugular venograms and pressure monitoring confirmed a narrowed jugular foramen in all patients, without any elevation of the venous pressures in a control group. The authors concluded that in patients with achondroplasia, intracranial venous sinus hypertension secondary to jugular foramen stenosis—and in some cases jugular vein stenosis at the thoracic inlet—is the cause of hydrocephalus. Interestingly, none of these patients were found to have any obstruction of CSF or delay in transit of contrast materials from the ventricular system to the basal cisterns, spinal canal, and into the subarachnoid space over the hemispheres. However, in a prior study by our group6 and a case report by Miyamoto et al.,14 several patients were noted to have decreased or obliterated CSF flow at the cervicomedullary junction as demonstrated using MR CSF flow studies, presenting the possibility that at least in some patients with foramen magnum stenosis there may be additional factors leading to ventriculomegaly or hydrocephalus. Additionally, in both the study by Steinbok et al. and Miyamoto et al., there was a compensatory increase in occipital and marginal sinus flow as well as condylar emissary vein dilation in the presence of jugular foraminal stenosis. In our case series we questioned whether one of the alternative pathways for venous outflow in these patients may be through the dural venous channels at the cervicomedullary junction, and whether performing a foramen magnum decompression in patients with both foramen magnum and jugular venous stenosis, these accessory venous outflow pathways, may play a significant role in providing alternative pathways for venous outflow and serve to lower intracranial venous pressure following foramen magnum decompression. Such alternative pathways between the cervicomedullary junction and cervical dural anastomoses were not directly measured in Steinbok et al.'s seminal work.22

In this paper we review our clinical experience with the surgical treatment of symptomatic foramen magnum stenosis over the past 11 years for the presence or absence of dynamic cervicomedullary compression. We demonstrate that there is a risk of dynamic cord compression and obstruction of CSF flow at the skull base in children with achondroplasia. This phenomenon may be due to bowing of the C1–2 anterior ligamentous complex. We postulate that this phenomenon may not only result in compression of the cervicomedullary junction, or obstruction of CSF flow, but may also result in exacerbating intracranial venous hypertension secondary to compression of outflow thru the cervical dural venous plexus. The technique we used to perform a duroplasty was that of scoring the external leaf of the dura at the foramen magnum and removing thickened posterior cervicomedullary ligament following a suboccipital craniectomy. By doing so, we avoided sacrificing dural venous anastomosis between cranial dural venous channels and spinal venous channels. Our results suggest, but do not provide definitive evidence, that these anastomoses may serve an important function in patients with achondroplasia who have elevated intracranial venous pressures due to stenosis at the level of the jugular foramen. Most of our patients who presented with a full fontanel had subjective improvement in preoperative signs and symptoms without a need for placement of a VP shunt. This improvement may also be a result of improved CSF flow dynamics, but it is difficult to explain any improvement of intracranial pressure accompanying hydrocephalus without a mechanism that includes improvement in venous drainage through venous anastomoses. Finally, it remains to be determined whether isolated dynamic cervicomedullary compression in patients with achondroplasia is an appropriate indication for surgical decompression.

Conclusions

Dynamic cervicomedullary compression is a phenomenon that, although previously described in the literature, has been incompletely explored. This retrospective, single-surgeon, single-institution study represents the largest series to date examining the diagnostic utility of obtaining dynamic cervical imaging in symptomatic patients with achondroplasia. Although further study is needed to address the full diagnostic utility of this imaging modality, there is promise that such dynamic imaging may provide a useful adjuvant diagnostic tool of investigation for a subset of symptomatic patients with unremarkable neutral cervical spine MRI studies.

Disclosure

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author contributions to the study and manuscript preparation include the following. Conception and design: Mukherjee, Danielpour, Rimoin. Acquisition of data: Mukherjee, Danielpour. Analysis and interpretation of data: Mukherjee, Danielpour. Drafting the article: Mukherjee, Danielpour, Krakow, Rimoin. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Danielpour. Statistical analysis: Mukherjee. Administrative/technical/material support: Mukherjee, Danielpour, Pressman, Krakow. Study supervision: Danielpour, Pressman, Krakow, Rimoin.

This article contains some figures that are displayed in color online but in black-and-white in the print edition.

References

If the inline PDF is not rendering correctly, you can download the PDF file here.

Article Information

Address correspondence to: Debraj Mukherjee, M.D., M.P.H., Maxine Dunitz Neurosurgical Institute, Department of Neurosurgery; Cedars-Sinai Medical Center, 8631 W. 3rd St., Ste. 800 East, Los Angeles, CA 90048. email: debraj.mukherjee@cshs.org.

Please include this information when citing this paper: published online June 27, 2014; DOI: 10.3171/2014.5.PEDS12614.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Activating mutations in FGFR3 within chondrocytes can lead to spinal stenosis, central sleep apnea, or hydrocephalus by decreasing the relative rate of endochondral bone formation.

  • View in gallery

    Primary measurements made using sagittal MR images of the cervical spine in neutral (A and B) and flexed (C) positions included the narrowest portion of the cervical spinal canal (green line), the spinal cord diameter at the cervicomedullary junction (red line), and thickness of the anterior ligamentous complex (blue line). These measurements regularly changed in the flexed versus neutral positions.

  • View in gallery

    Dynamic T2-weighted (A and C) and cine (B and D) sagittal MR images of the cervical spine demonstrating cervical stenosis greater in flexion (A and B) than in extension (C and D).

  • View in gallery

    Preoperative (A and B) and postoperative (C and D) T2- weighted (A and C) and cine (B and D) sagittal MR images obtained in a single patient in the neutral position illustrating decompression (C) and improved flow (D) postoperatively.

  • View in gallery

    The Evans ratio is defined as the maximum ventricular width (red line) divided by the largest biparietal distance between the inner tables of the skull (green line). An Evans ratio of at least 0.3 may be consistent with a diagnosis of hydrocephalus.

References

1

Aryanpur JHurko OFrancomano CWang HCarson B: Craniocervical decompression for cervicomedullary compression in pediatric patients with achondroplasia. J Neurosurg 73:3753821990

2

Bagley CAPindrik JABookland MJCamara-Quintana JQCarson BS: Cervicomedullary decompression for foramen magnum stenosis in achondroplasia. J Neurosurg 104:3 Suppl1661722006

3

Bland JDEmery JL: Unexpected death of children with achondroplasia after the perinatal period. Dev Med Child Neurol 24:4894921982

4

Carson BWinfield JWang HReid CMcPherson RKopits S: Surgical management of cervicomedullary compression in achondroplastic patients. Nicoletti BAsconi EMcKusick VA: Human Achondroplasia New YorkPlenum Press1988. 207214

5

Dandy WE: Hydrocephalus in chondrodystrophy. Bull Johns Hopkins Hosp 32:5101921

6

Danielpour MWilcox WRAlanay YPressman BDRimoin DL: Dynamic cervicomedullary cord compression and alterations in cerebrospinal fluid dynamics in children with achondroplasia. Report of four cases. J Neurosurg 107:6 Suppl5045072007

7

Depresseux JCCarlier GStevenaert A: CSF scanning in achondroplastic children with cranial enlargement. Dev Med Child Neurol 17:2242281975

8

Francomano CACarson BSeidler AJames CMatthew CMiller D: Morbidity and mortality in achondroplasia: efficacy of prospective evaluation and surgical intervention. Am J Hum Genet 53:A1121993

9

Haar FLMiller CA: Hydrocephalus resulting from superior vena cava thrombosis in an infant. Case report. J Neurosurg 42:5976011975

10

Hecht JTFrancomano CAHorton WAAnnegers JF: Mortality in achondroplasia. Am J Hum Genet 41:4544641987

11

Horton WARotter JIRimoin DLScott CIHall JG: Standard growth curves for achondroplasia. J Pediatr 93:4354381978

12

Hunter AGBankier ARogers JGSillence DScott CI Jr: Medical complications of achondroplasia: a multicentre patient review. J Med Genet 35:7057121998

13

King JAVachhrajani SDrake JMRutka JT: Neurosurgical implications of achondroplasia. A review. J Neurosurg Pediatr 4:2973062009

14

Miyamoto JTatsuzawa KSasajima HMineura K: Usefulness of phase contrast cine mode magnetic resonance imaging for surgical decision making in patients with hydrocephalus combined with achondroplasia. Case report. Neurol Med Chir (Tokyo) 50:111611182010

15

Mueller SM: Enlarged cerebral ventricular system in infant achondroplastic dwarf. Neurology 30:7677691980

16

Mueller SMBell WCornell Sde Hamsher KDolan K: Achondroplasia and hydrocephalus. A computerized tomographic, roentgenographic, and psychometric study. Neurology 27:4304341977

17

Pauli RMHorton VKGlinski LPReiser CA: Prospective assessment of risks for cervicomedullary-junction compression in infants with achondroplasia. Am J Hum Genet 56:7327441995

18

Pierre-Kahn AHirsch JFRenier DMetzger JMaroteaux P: Hydrocephalus and achondroplasia. A study of 25 observations. Childs Brain 7:2052191980

19

Reid CSPyeritz REKopits SEMaria BLWang HMcPherson RW: Cervicomedullary compression in young patients with achondroplasia: value of comprehensive neurologic and respiratory evaluation. J Pediatr 110:5225301987

20

Rimoin DL: Cervicomedullary junction compression in infants with achondroplasia: when to perform neurosurgical decompression. Am J Hum Genet 56:8248271995

21

Rimoin DL: The chondrodystrophies. Adv Hum Genet 5:11181975

22

Steinbok PHall JFlodmark O: Hydrocephalus in achondroplasia: the possible role of intracranial venous hypertension. J Neurosurg 71:42481989

TrendMD

Metrics

Metrics

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 166 166 28
PDF Downloads 165 165 14
EPUB Downloads 0 0 0

PubMed

Google Scholar