This issue of CDR will qualify for 2 ABR Self-Assessment Module SAM (SA-CME) credits. See page 7 for more information. Volume 38 • Number 13 June 30, 2015 Imaging Miscues in Pediatric Headache Lee Nakamura, MD, Michael J. Paldino, MD, and Jeremy Y. Jones, MD This module meets the American Board of Radiology’s (ABR’s) criteria for self-assessment toward the purpose of fulfilling requirements in the ABR Maintenance of Certification program. Please note that in addition to the SA-CME credits, subscribers completing the activity will receive the usual ACCME credits. After participating in this activity, the radiologist should be better able to diagnose causes of headache in the pediatric population, and consequently to avoid diagnostic imaging miscues. cerebellar tonsillar ectopia as a manifestation of Chiari I CME Category: Pediatric Radiology Subcategory: Neuroradiology malformation, and its mimics; (2) subtle imaging fi ndings of Modality: MRI vascular etiologies for headache, including circle of Willis vasculopathy and dural sinus thrombosis; and (3) typical imaging features of migraine variants presenting in the pedi- Key Words: Imaging of Pediatric Headache, Pediatric atric population, including hemiplegic and ophthalmoplegic Headache migraine. Much has been written regarding the indications for imag- Headache With Chiari I Malformation and Its Mimics ing in pediatric headache to facilitate the detection of poten- Chiari I malformation conventionally is defi ned as cer- tially catastrophic structural lesions (i.e., tumors and ebellar tonsillar descent below the level of the foramen hydrocephalus). Detection of such lesions is typically magnum by at least 5 mm, in the absence of intracranial straightforward with CT or MRI. Imaging correlates for cer- mass lesions, hydrocephalus, and cerebral or cerebellar tain well-described causes of pediatric headache, however, edema. As so defi ned, Chiari I malformation is noted in up may be more subtle and, therefore, potentially overlooked. to 3.6% of children referred for head MRI.1 Symptomatic Furthermore, the overlap of imaging patterns may result in patients with Chiari I malformation often present with head- the potential for misinterpretation. The purpose of this arti- aches that are short in duration, occipital or nuchal in location, cle is to highlight some of the entities in which imaging fi nd- and exacerbated by the Valsalva maneuver. Management ings are subtle and/or overlooked in this population of of symptomatic patients with Chiari I malformation is children with headache. In particular, we discuss: (1) inferior surgical, consisting of posterior decompression with infe- rior occipital craniectomy, C1 laminectomy, and possibly Dr. Nakamura is Pediatric Neuroradiology Fellow, Texas Children’s Hospital; duraplasty. Dr. Paldino is Assistant Professor, Baylor College of Medicine and a Neuro- radiologist, Texas Children’s Hospital; and Dr. Jones is Assistant Professor, Baylor College of Medicine and Neuroradiology Section Chief, Singleton Department of Radiology, Texas Children’s Hospital, 6701 Fannin St, Ste 470, Houston, TX Symptomatic patients with Chiari I malformation 77030; E-mail: [email protected] often present with headaches that are short in The authors and all staff in a position to control the content of this CME activity duration, occipital or nuchal in location, and and their spouses/life partners (if any) have disclosed that they have no relation- exacerbated by the Valsalva maneuver. ships with, or fi nancial interests in, any commercial organizations pertaining to this educational activity. Lippincott Continuing Medical Education Institute, Inc., is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. Lippincott Continuing Medical Education Institute, Inc., designates this enduring material for a maximum of 2 AMA PRA Category 1 Credits™. Physicians should only claim credit commensurate with the extent of their participation in the activity. To earn CME credit, you must read the CME article and complete the quiz and evaluation on the enclosed answer form, answering at least seven of the 10 quiz questions correctly. This continuing medical education activity expires on June 29, 2016. 1 CCDRv38n13.inddDRv38n13.indd 1 55/6/15/6/15 22:17:17 AAMM A subgroup of patients with Chiari I malformation, recently dens, reduced craniocervical angle, basilar invagination, platy- described as “complex Chiari malformation,” may require addi- basia, and atlanto-occipital assimilation.2 tional posterior occipitocervical fusion and/or ventral decom- Peg-like cerebellar tonsils meeting these measurement cri- pression for optimal therapy. In addition to cerebellar tonsillar teria are not specifi c for Chiari I malformation. They also may descent, these children with complex Chiari malformation are occur in the setting of intracranial hypotension. The headache identifi ed by brainstem descent, with an obex position below in patients with intracranial hypotension is characteristically the level of the foramen magnum and a dorsal cervicomedullary orthostatic, increased with sitting or standing, and improved hump (Figure 1). This constellation of findings has been in the supine position. Intracranial hypotension results from referred to as “Chiari 1.5.” Osseous anomalies of the craniocer- low cerebrospinal fl uid (CSF) pressure/volume of any cause, vical junction commonly are demonstrated in patients with including from a persistent CSF leak in the spine. Although complex Chiari malformation, including retrofl exion of the most commonly seen after violation of the spinal dura (e.g., after lumbar puncture), leaks may be spontaneous and are thought to result from tearing at a site of congenital or acquired weakness of the dura, such as a spinal diverticulum or dural ectasia. As such, patients with connective tissue disorders may be at increased risk for spontaneous intracranial hypotension. In our practice, overshunting is probably the most common cause of cerebellar tonsillar descent from intracranial hypo- tension. Regardless of the cause, treatment of intracranial hypotension with surgical posterior fossa decompression is inappropriate. Therapeutic options to treat the cause of the spi- nal leak include epidural blood patch, fi brin glue injection, or surgery.3 Although potentially similar in appearance to Chiari I malformation on MRI, often there are additional MR signs that suggest the diagnosis of intracranial hypotension. These additional MR signs include diffuse, smooth pachymeningeal enhancement; venous sinus distension, enlargement of the pituitary gland; and descent of the brain (including reduction in size or effacement of the prepontine or interpeduncular cisterns, inferior displacement of the optic chiasm, and descent of the iter, which is the entrance of the cerebral aqueduct) (Figure 2). Patients with connective tissue disorders may be at increased risk for spontaneous intracranial hypotension. Figure 1. Complex Chiari malformation in a 4-year-old boy with Idiopathic intracranial hypertension also can be associated recurrent headaches and vomiting for 3 months. Sagittal with inferior cerebellar tonsillar ectopia, with the tonsils T1-weighted MR image demonstrates pointed cerebellar tonsils extending 5 mm below the foramen magnum in as many as extending to the posterior arch of C1, an obex below the foramen 21% of individuals in a recent adult series.4 Headache is the magnum, a dorsal cervicomedullary hump (long arrow), a short most common presentation and tends to be variable in char- clivus (asterisk), and basilar invagination (arrowhead). The obex is the point on the midline of the dorsal surface of the medulla acter. The diagnosis usually is made by the constellation of oblongata that marks the caudal angle of the fourth ventricle. Note headache, papilledema, elevated opening CSF pressure, and syrinx in the cervical cord. absence of an intracranial mass lesion or hydrocephalus. Its The continuing education activity in Contemporary Diagnostic Radiology is intended for radiologists. EDITOR: Robert E. Campbell, MD, Clinical Professor of Radiology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania Contemporary Diagnostic Radiology (ISSN 0149-9009) is published bi-weekly by Lippincott Williams & Wilkins, Inc., 16522 Hunters Green Parkway, Hagerstown, MD 21740-2116. Customer Service: Phone (800) 638-3030; Fax (301) 223-2400; E-mail: [email protected]. Visit our website at LWW.com. Publisher, Randi Davis. EDITORIAL BOARD: Teresita L. Angtuaco, MD Bruce L. McClennan, MD Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. Priority Postage paid at Hagerstown, MD, and at George S. Bisset III, MD Johnny U. V. Monu, MBBS, Msc additional mailing offi ces. POSTMASTER: Send address changes to Contemporary Diagnostic Radiology, Subscription William G. Bradley Jr., MD, PhD Pablo R. Ros, MD, MPH, PhD Dept., Lippincott Williams & Wilkins, P.O. Box 1600, 16522 Hunters Green Parkway, Hagerstown, MD 21740-2116. Liem T. Bui-Mansfi eld, MD William M. 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