Ultrasound of the Neonatal Craniocervical Junction

Transcription

1 449 Ultrasound of the Neonatal Cranioervial Juntion envon C. Cramer 1 Sigrid Jequier2 ugustin M. O'Gorman2 To determine the value of ultrasound sanning of the ranioervial juntion in neonates via a posterior approah, we examined 50 infants with normal posterior fossae, 10 with ongenital abnormalities, and eight with intraranial hemorrhage. Good evaluation of the isterna magna, medulla, tonsils, vermis, ervial ord, and entral anal was possible in most ases. In nine patients with spinal dysraphism, all displayed a Chiari II malformation; of these, a kink at the medullary ord juntion was seen in six, and a erebellar peg was noted in four. In one ase, the Chiari malformation was onfirmed by myelography, and all nine patients had some of the intraranial features of Chiari II malformation seen via the standard anterior fontanelle approah. The 10th patient in this group had a quadrigeminal plate yst and gross hydroephalus. In another four infants, diffuse subarahnoid blood in the isterna magna was seen after reent intraventriular hemorrhage. further two of four patients with posthemorrhagi hydroephalus had loalized lots. Diret sanning at the ranioervial juntion was easily performed and allowed good evaluation of this area in normal infants and in patients with Chiari II malformation. This tehnique also allowed visualization of subarahnoid blood and lots obstruting the outlet of the fourth ventrile. This artile appears in the May/June 1986 issue of JNR and the July 1986 issue of JR. Reeived January 29, 1985; aepted after revision September 25, Presented at the annual meeting of the Soiety for Pediatri Radiology, oston, pril This work was supported in part by the MGill University-Montreal Children's Hospital Researh Institute. 1 Present address: Department of Radiology, Dr. Charles. Janeway Child Health Centre, Pleasantville, St. John 's, Nfld. 1 1R8, Canada. ddress reprint requests to. Cramer. 2 Department of Radiology, Montreal Children's Hospital and MGill University, 2300 Tupper Street, Montreal, Quebe, H3H 1 P3, Canada. JNR 7: , May/June /86/ merian Soiety of Neuroradiology The ranioervial juntion of the neonate has traditionally been assessed via the anterior fontanelle with ultrasound [1], by myelography [2], by omputed tomography [3], and more reently by magneti resonane [4]. Diret ultrasound sanning of the spinal anal in neonates and young infants has been widely reported [5-10], but detailed investigation of the ranioervial juntion has not. In the neonate, and espeially in the premature infant, the posterior arhes of the spinal anal are minimally ossified, allowing an exellent aousti window into this region [11]. To determine the appearane of the normal erviomedullary juntion, and partiularly the entral anal, 50 infants with normal ranioervial juntions were examined. These were ompared with 10 babies with ongenital abnormalities and eight with intraranial hemorrhage to assess the visualization of Chiari II malformation and to evaluate the blood in the isterna magna. Materials and Methods ll examinations were performed with a real-time setor sanner ( TL 1 DDD) using a 7.5 MHz transduer. Images were reorded on film via the built-in multiformat amera. The babies were sanned in the lateral deubitus position, preferably with the head flexed. If neessary, the examination was performed in the isolette. The transduer was plaed at approximately C 2 and angled upward and downward. Various angulations and positions were required for optimal visualization of all strutures from the lower ervial ord to the fourth ventrile. Early in the study five examinations were unsuessful beause of patient movement; subsequently, the examinations were usually performed when the babies were sleeping or postprandial. One examination was undertaken after sedation. The sonograms were performed on onseutive patients between September 1983 and May Ninety-four perent of the babies were in the neonatal unit at the Montreal Children's Hospital. Ultrasound examinations for both the normal and abnormal groups were

2 450 CRMER ET L. JNR :7, May/June 1986 Fig. 1.-Normal sagittal (), parasagittal (), and transverse sonograms (C) in a neonate viewed with the patient prone, showing the normal ranioervial juntion. The arrowheads outline the ervial ord. (m = isterna magna, v =vermis, t = tonsil, m = medulla, f = fourth ventrile.) requested mainly to investigate apnea, seizures, or ongenital abnormalities, or to study premature infants. Sagittal, parasagittal, and transverse images were obtained in 68 babies, 43 girls and 25 boys, ranging in age from 26 to 50 weeks [mean 39 ± 0.6 standard error of mean (S.E.)]. There were 50 infants with normal brain sans and normal ranioervial juntions whose ages ranged from 28 to 50 weeks (mean 39.5 ± 0.6 S.E.). Ten infants had ongenital abnormalities and ranged in age from 37 to 41 weeks (mean 40 ± 0.04 S.E.). Nine of this group had spinal dysraphism. nother eight babies, ranging in age from 26 to 40 weeks (mean 32.3 ± 2.0 S.E.), had intraranial hemorrhage. Results Norma/ Patients The ervial ord and subarahnoid spae and the isterna magna were identified in all normal infants and were seen well in most ases (78%). The isterna magna provides an aousti window. When it was learly identified, the medulla was seen well (70% of examinations). The fourth ventrile was evident in 44% of the ases, but required steep angulation of Fig. 2.-Normal sagittal sonogram of the ranioervial juntion in a neonate demonstrating the entral anal as a distint hannel proximally (arrowheads) and as a single line distally (straight arrow). The vertebral bodies are seen anteriorly (urved arrows ).

3 D Fig. 3.-, Sagittal sonogram at ranioervial juntion in a patient with a meningomyeloele demonstrating the juntion of the medulla and spinal ord with a spur (arrowhead). The san is orientated vertially for omparison with the myelogram. The ervial ord with its entral anal (straight arrow) is seen inferior to the larger sonoluent med ulla. The isterna magna (em) is filled with erebellar tissue. S, Myelogram on the same patient demonstrating the spur (arrowhead) and erebellar tissue (straight arrow). C, Transverse sonogram of the ervial ord (arrowhead) viewed with the patient prone demonstrating the entral anal (arrow). D, Transverse sonogram in region of the herniated medulla (arrowheads) viewed with the patient prone demonstrating the eentri anal (arrow).

4 452 CRMER ET L. JNR :7, May/June 1986 Fig. 4.-Sagittal sonogram of the ranioervial juntion in another patient with a meningomyeloele demonstrating the medullary kink (straight arrow) and a erebellar peg (C P) in the region of the isterna magna (urved arrows). the transduer to be visualized. The vermis of the erebellum was seen in 80% of the examinations as a entral ehodense area immediately inferior to the fourth ventrile (Fig. 1). Its density is similar to that seen on sonography performed via the anterior fontanelle. The more sonoluent erebellar tonsils were evident on either side (in 60% of examinations), and the erebellar folia, lateral to the tonsils, were seen in 40% of the ases. Visualization of the erebellar folia also required steep lateral angulation of the transduer. The arterial pulsations of the posterior inferior erebellar artery in the isterna magna were seen in 64% of normal infants. The entral anal of the ervial ord was visible as a distint hannel from the obex to approximately C 2 in 80% of the ases, measuring no more than 1 mm in diameter. Distally the anal appeared as a single line of ehoes (Fig. 2). In addition, the vertebral bodies were evident anterior to the ord and subarahnoid spae in the ervial region, whih was useful to determine the level of the anal. Optimal visualization was generally obtained in premature infants, but adequate examinations were obtained in all babies up to 2 months old who remained quiet during sanning. The variation in image quality was partly due to age, but was also due to individual variation in anatomy and development. However, visualization of the fourth ventrile and medulla was not signifiantly inreased in infants younger than 35 weeks of age ompared with those who were older. Congenital bnormalities Of the 10 infants with ongenital abnormalities, nine had a Chiari " malformation and one had a quadrigeminal plate yst. ll nine with spinal dysraphism had isterna magna obliteration. In seven of the nine (77%) the juntion of the ord and medulla was seen in the ervial region. Three were at C 2, two at C 2/ 3, and two at C 4 level. The ervial ord and its entral anal were easily identified in the lower ervial anal. The medulla, with its eentri anal, is wider and more uniformly sonoluent than the ervial ord. The posterior portion of its anal is formed by either the posterior wall of the elongated fourth ventrile or by a erebellar peg (Fig. 3). The medullary anal was only learly visible in three patients. Fig. S.-Sagittal sonogram of the ranioervial juntion in the patient with a quadrigeminal plate yst. There is a wide defet at the foramen magnum, whih is filled with herniated erebellar tissue (arrowheads). In addition, a erviomedullary spur or kink was seen at this level in six of seven infants (86%) whose juntions were visible in the ervial region (Fig. 4). Posterior dilatation of the fourth ventrile was not seen in any ase, but the kink overlapped the upper ord in four patients. In an additional four ases, a erebellar peg was also seen at (in two patients) or below (in two patients), the foramen magnum. None of these features was seen with the standard anterior fontanelle approah. Four of these babies had repeat examinations, whih onfirmed the findings. The ranial sonographi findings seen via the anterior fontanelle approah, in Chairi " malformation, inlude hydroephalus with pointing of the frontal horns, asymmetry of the lateral ventriles, relative enlargement of the oipital horns ompared with the frontal horns, partial absene of the septum pelluidum, abnormalities of the third ventrile with a prominent massa intermedia, and a V-shaped and low tentorium erebellum [12]. In varying degrees, some of these features were present in all nine patients. In one ase, the Chiari " malformation was onfirmed by myelography. One neonate had severe hydroephalus due to quadrigeminal plate yst, whih was eventually diagnosed on CT ventriulography. There was little identifiable brain tissue on sonographs via the anterior fontanelle. Diret sanning at the ranioervial juntion showed the harateristi pattern of the erebellum in this region with obliteration of the isterna magna, indiating tonsillar herniation (Fig. 5). Intraventriular Hemorrhage and Its Sequelae In eight patients with intraventriular hemorrhage, four had the hemorrhage 1 to 3 days before the examination and four had it between 4 days and 3 weeks previously. Subarahnoid blood or lot was identified in four premature infants with reent intraventriular hemorrhage. In the aute phase, the blood was ehogeni in the subarahnoid spae and isterna

5 JNR:7, May/June 1986 NEONTL CRNIOCERVICL JUNCTION 453 Fig. 6.-, Coronal sonogram of the head demonstrating intraventriular, germinal matrix and intraparenhymal extension of hemorrhage., Sagittal sonogram at ranioervial juntion, performed at the same time as in, demonstrating extension of hemorrhage into the isterna magna (arrowhead) and premedullary istern (straight arrow). C, Sagittal sonogram at ranioervial juntion performed 3 days later showing the premedullary istern, whih is now o sonoluent (straight arrows) but ontains some ehoes indiating the presene of a resolving hematoma. Residual loalized lot is present in the isterna magna (arrowhead). D, Transverse sonogram of isterna magna (arrowheads) showing the posterior inferior erebellar artery (arrow). During the examination, the artery was noted to pulsate adjaent to the resolving lot (l) (m = medulla). magna but it later beame hypoehoi and formed loalized lots, as seen with intraventriular hemorrhage (Fig. 6). The most severe of these ases eventually required shunting for posthemorrhagi hydroephalus. ll four patients with remote hemorrhage developed hydroephalus. In one, lots were shown protruding into the distal end of the fourth ventrile, and, in another, they were within a dilated fourth ventrile and isterna magna (Fig. 7). fter the development of hydroephalus, the isterna magna was generally ompressed or effaed. The subarahnoid hemorrhage was not identified on routine anterior fontanelle sanning in any of these ases. In those ases with remote hemorrhage and hydroephalus, the degree of dilatation of the fourth ventrile and the extent of ommuniation with the isterna magna, as well as the presene of blood lots, were better defined than via the anterior fontanelle approah. Disussion Sonography of the spine in both infants and adults is a well-reognized tehnique. In infants the proedure an dem-

6 454 CRMER ET L. JNR :7, May/June 1986 Fig. 7.- and, Sagittal ana transverse sonogram at ranioervial juntion in a premature infant with remote intraventriular hemorrhage and hydroephalus demonstrating a large ehogeni lot (arrow) protruding into the distal end of a dilated fourth ventrile (I). C, Follow-up examination performed 6 weeks after ventriuloperitoneal shunting demonstrating a redution in size of the fourth ventrile (I) and resolution of the lot. on strate a wide range of abn::>rmalities [5-13]. Goodwin and Quisling [1] desribed the neonatal isterna magna on sonography done via the anterior fontanelle. The isterna magna area has also reently been desribed on CT examination [3]. However. there has been no detailed report of the ranioervial juntion studied by sonography performed via the posterior approah. The tehnique to assess the raniovertebral juntion in neonates by sonography is easy to perform and is reproduible. Our study demonstrates that the normal isterna magna, ervial ord, medulla, tonsils, and vermis an be seen in most ooperative infants. The diameter of the entral anal an be measured and should be no greater than 1 mm. For babies with ongenital abnormalities of the spine elsewhere, this examination an onfirm or exlude the presene and extent of Chiari II malformation quikly and more aurately than an sonography done via the anterior fontanelle. It is partiularly useful in those infants with lower ranial-nerve signs. The presene of a erebellar peg and a erviomedullary spur, whih has been well desribed pathologially and on myelography [12], an also be visualized. The erebellar peg is a downward herniation that may ontain the nodulus, uvula, and pyramis in the midline. The erviomedullary spur is aused by bukling of the medulla on the upper ervial ord due to the herniation. This method of evaluating the raniovertebral juntion may be helpful in determining the suitability of a isternal or C 1 -C 2 punture for myelographi visualization of the spinal anal in ertain spinal dysraphi states. It may also be an aid in determining the potential benefits of deompressing the hindbrain by upper ervial laminetomy and in evaluating the posterior fossa strutures in infants with omplex brain abnormalities. Sonography via the posterior approah is also useful in infants with intraranial hemorrhage. Subarahnoid blood was learly seen in four infants with reent intraventriular hemorrhage. The amount and age of the subarahnoid hemorrhage required for visualization of blood in the isterna magna is unknown. To find out would require a detailed study with omparison to CT and lumbar punture findings. It is possible that a small-onvexity subarahnoid hemorrhage may be overlooked with the posterior approah. nterior fontanelle sonography has been disappointing in diagnosing subarahnoid hemorrhage. In patients with posthemorrhagi hydroephalus, lots were observed in the fourth ventrile and isterna magna. Serial sonograms showed the progression or resolution of these lesions. method of treating posthemorrhagi hydroephalus used oasionally is serial lumbar punture rather than immediate ventriuloperitoneal shunting [14]. In those babies with obstrution of the fourth ventrile aused by lot, repeated lumbar punture for ontrol of hydroephalus is un-

7 JNR :7, May/June 1986 NEONTL CRNIOCERVICL JUNCTION 455 likely to sueed and may be dangerous. Visualization of these lots may help determine how the hydroephalus should be ontrolled. In onlusion, this study showed that ultrasound examination of the neonatal ranioervial juntion via the posterior approah is easy to perform, yields good anatomial definition in the majority of infants, and is helpful in assessing infants with ongenital malformations-partiularly Chiari II malformations-and ases of intraventriular and subarahnoid hemorrhage. CKNOWLEDGMENT We thank Mihel Le lan for photography. REFERENCES 1. Goodwin L, Quisling RG. The neonatal isterna magna: ultrasoni evaluation. Radiology 1983;149 : Johnson S, Nayanar VV, Jones RFC. Metrizamide myelography in spinal dysraphism. ustralas RadioI1980;24 : Resjo 1M, Harwood-Nash DCF, Fitz CR, Chuang SH. Normal ord in infants and hildren examined with omputed tomography metrizamide myelography. Radiology 1979;130 : Modi MT, Weinstein MD, Pavliek MS, oumphrey F, Starnes D, Duhesneau PM. Nulear magneti resonane imaging of the spine. Radiology 1983;148: raun IF, Raghavendra N, Kriheff II. Spinal ord imaging using real-time high resolution ultrasound. Radiology 1983 ;147: Naidih TP, Fernbak SK, MLone DG, Shkolnik. Sonography of the audal spine and bak: ongenital anomalies in hildren. JNR 1984;5 : , JR 1984;142: Miller JH, Reid S, Kemberling CR. Utilization of ultrasound in the evaluation of spinal dysraphism in hildren. Radiology 1982;143: Raghavendra M, Epstein FJ, Pinto RS, Subrananyan R, Greenberg J, Nutrih JS. Tethered spinal ord: diagnosis by high resolution real-time ultrasound. Radiology 1983;149 : Sheible W, Zames HE, Leopold GR, Hilton SVM. Oult spinal dysraphism in infants: sreening with high resolution, real-time ultrasound. Radiology 1983;146 : Kangarloo H, Gold RH, Diament MJ, oehat MI, arett C. Highresolution spinal sonography in infants. JNR 1984;5: , JR 1984;142 : Jequier S, Cramer, O'Gorman M. Ultrasound of the spinal ord in neonates and infants. nn Radiol (PariS) 1985;28: 3-4, abok DS, Han K. Cranial sonographi findings in meningomyeloele. JR 1981 ;136 : Naidih TP, MLane DG, Fulling KH. The Chiari II malformation: part IV. The hindbrain deformity. Neuroradiology 1983;25: Papile L, urstein J, urstein R, Kofflen H, Koofs, Johnson J. Post hemorrhagi hydroephalus in low-birth-weight infants: treatment by serial lumbar puntures. J Pediatr 1980;97 :