CT/MRI enhancement patterns after cranial surgery / intervention in children

Transcription

1 CT/MRI enhancement patterns after cranial surgery / intervention in children Poster No.: C-1433 Congress: ECR 2015 Type: Authors: Keywords: DOI: Educational Exhibit S. Deftereos, S. Foutzitzi, P. Argyropoulou, P. Prassopoulos; Alexandroupolis/GR Pediatric, CT, MR, Diagnostic procedure, Cancer, Cerebrospinal fluid, Cysts /ecr2015/C-1433 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 18

2 Learning objectives To describe the CT and MR imaging of the postoperative skull and brain in children. To illustrate early and delayed postoperative contrast enhancement (CE) patterns of the postoperative skull and brain in children. To differentiate the expected and clinically irrelevant enhancement from a residual pathology and/or from surgical complication. Normal anatomy. (Fig. 1, 2) The scalp extends anteroposteriorly from the supraorbital ridge to the superior nuchal line and laterally to the zygomatic arch and external auditory meatus. The scalp is composed of five layers: 1. the skin, 2. subcutaneous tissue, 3. galea aponeurotica, 4. loose areolar connective tissue, 5. pericranium, and it contains three primary muscle groups: 1. frontalis, 2. occipitalis and 3. temporalis. The skull vault, also called calvaria, contains the diploë (Fig. 1) which is a layer of cancellous bone between the inner and the outer tables of calvaria (cortical bone). At MR imaging, the inner and outer tables have very low signal intensity, in all sequences. The appearance of the diploë depends on the age of the patient: T1-weighted images: low signal intensity (first 2 decades of life) and high signal intensity thereafter (fatty conversion of the diploic marrow). The dura mater (a hard double-layered membrane): The outer layer is formed by the periosteum (of the inner table of the calvaria) and The inner layer is the dura mater proper. The two layers are continuous except: at the dural venous sinuses and Page 2 of 18

3 at the regions where the inner layer projects inward to form the tentorium cerebelli, the falx cerebri and cerebelli, and the diaphragm sellae. On MR images, the dura mater typically appears as low-signal-intensity segments and it enhances after intravenous contrast material injection (it lacks of blood-brain barrier). Enhancement typically is most prominent in the segments over the convexities. The two deeper meningeal layers (arachnoid and pia mater) are not normally visible at imaging (Fig.2). Images for this section: Fig. 1: Normal scalp anatomy [male 6yo]. Axial CT image obtained at the level of the temporal fossa shows the skin, which appears as a linear hyperattenuating structure (arrowhead), and subcutaneous tissue, which appears as a thicker layer of fatty attenuation (thick arrow). The temporalis fascia appears as a thin line of increased attenuation (straight arrow), and the subgaleal layer of loose areolar tissue contains fat (curved arrow) and the temporalis muscle (star). Note the inner and outer tables of calvaria (orbit's level) as well defined and with very high attenuation, as well as the diploic space with lower attenuation. The galea aponeurotica is a layer of thick fibrous tissue that Page 3 of 18

4 is continuous with the occipitofrontalis and auricularis muscles. The temporalis muscle lies deep to the temporalis fascia and arises from the temporal fossa pericranium which is continuous with the galea superiorly. Subgaleal fluid collections can be extensive and may cross skull sutures (like intracranial subdural fluid collections). Fig. 2: Normal scalp anatomy [male 5yo]. Axial MR image obtained at the level of Sylvian fissures. Note the enhancement of pia matter. Page 4 of 18

5 Background Interpretation of early and/or late postoperative CT and MR imaging following cranial surgery in children is often cumbersome. Residual pathology or surgical complications may exhibit contrast enhancement (CE). However, CE related to an uncomplicated surgery is of no clinical significance. Complications that are associated with all neurosurgical procedures include infection, skull fracture, and hemorrhage. neurosurgical procedures: burr holes craniotomy (six standard types [table 1]) - craniectomy - cranioplasty ventricular shunting. Images for this section: Page 5 of 18

6 Fig. 4: Table 1. The type of craniotomy is depending to the desired intracranial content accessibility. Page 6 of 18

7 Findings and procedure details Burr holes (Fig 4, 5) Usually complications associated with burr holes is the potential to plunge the drill into the cranium (less common with with automatic power drills). T2-weighted MR images may reveal an area of high-signal-intensity oedema underlying the burr hole (the "mushroom" sign). Haemorrhagic complications of plunging (intracerebral hematoma, cortical laceration, extradural hematoma, subdural hematoma, intraventricular hemorrhage) contribute to increased morbidity and mortality and of course are causes for a prolonged postoperative recovery period. A complication that may occur in children and particularly in infants is the formation of an enlarging pseudomeningocele (as a result from a growing burr hole). Craniotomy Craniotomy (surgical removal of a portion of the skull). The bone flap is replaced at the end of the procedure and thereafter is identified according to its location (frontal, bifrontal, parietal, occipital) (Fig.6). In the early postoperative period, scalp swelling due to a mixture of oedematous fluid, hemorrhage, cerebrospinal fluid (CSF), and air, in varying amounts, is common findings. The swelling typically resolves over several weeks (Fig. 7). Specific patterns and sites of CE are expected after an uncomplicated cranial surgery or ventricular shunting (Fig. 12). Enhancement is seen earlier and lasts longer on MRI than it does on CT. CE may be seen in the traumatized temporalis muscle in the early postoperative days (pterional craniotomy). Neovascular granulation tissue formed between the bone flap and the calvaria may enhance within the 1st year after surgery (Fig. 8, 9). The dura mater enhances in a smooth linear pattern as soon as 9 hours postoperatively, enhancement can last up to 40 years and almost always occurs in the portion of the dura mater that is deep to the flap (frequently widespread) (Fig 9). After brain tissue resection, the surgical margins may begin to enhance within 17 hours (Fig. 10). They initially appear as thin linear areas of enhancement that increase with time# by the 6th postoperative day they are thicker and nodular. This pattern of brain enhancement usually resolves within 1 month after surgery (Fig. 11). Images for this section: Page 7 of 18

8 Fig. 3: Burr hole [boy 14yo]: Bone-dust-packed burr hole in a 14 year-old boy, 1 day after "drilling". Page 8 of 18

9 Fig. 5: Burr hole (female 13 yo): Axial CT image obtained with both brain and bone algorithm shows typical burr hole with small amount of air. Page 9 of 18

10 Fig. 6: Bone flap remodeling in a 18-year-old boy 20 months after craniotomy (car accident). Axial bone algorithm CT image shows the rounded and remodeled margins of the craniotomy (arrows) and the titanium clamps (arrows) used to hold the left-sided acrylic flap (thick arrow) in place. Page 10 of 18

11 Fig. 7: Boy 15yo, the early postoperative period, before and after CM reveals scalp swelling due to a mixture of oedematous fluid, hemorrhage, cerebro spinal fluid (CSF), and air, in varying amounts. The swelling typically resolves over several weeks. Page 11 of 18

12 Fig. 8: Subdural empyema [boy 11 yo] due to unsatisfactory treatment of sinusitis. Page 12 of 18

13 Fig. 9: Same patient with Fig 8: Dural enhancement in 6 months after empyema's surgical treatment. Axial T1W and axial T1W-gadolinium-enhanced MR images show smooth enhancement of the thickened left dura mater (compare with the contralateral dura mater). Page 13 of 18

14 Fig. 10: Haemorragic tumor [girl 9mo] causes hydrocephalus (initial CT). Axial T1W and axial T1W-gadolinium-enhanced MR images after 1 month of brain tissue resection, reveal the surgical margins with smooth and somewhat nodular enhancement (arrow). Page 14 of 18

15 Fig. 11: Pylocytic astrocytoma [boy 15yo].Pre-surgical MR and post-surgical MRI in same level and in axial axial T1W-gadolinium-enhanced MR images after brain tissue resection (1 month, 7, 27 and 53 monthes), reveal the surgical margins with smooth and somewhat nodular enhancement resolving gradually after surgery (arrow). Page 15 of 18

16 Fig. 12: Postsurgical (craniopharyngioma) ventricular shunting: Note the enhancement at the tip of the shunt (xial T1W and axial T1W-gadolinium-enhanced MR images) and the surround gliosis (T2W image). The findig should not be considered abnormal while the dura mater is normal. Follow-up MRI (eg after year) is sufficient. Page 16 of 18

17 Conclusion Knowledge of expected CT and MR enhancement patterns after a cranial intervention in children is fundamental to avoid misinterpretation. Personal information References 1. Rao CV, Kishore PR, Bartlett J, Brennan TG. Computed tomography in the postoperative patient. Neuroradiology 1980;19(5): Ruff RJ, Osborn AG, Harnsberger HR, Kubal WS. Extracalvarial soft tissues in cranial computed tomography: normal anatomy and pathology. Invest Radiol 1985;20(4): Akins PT, Guppy KH. Sinking skin flaps, paradoxical herniation, and external brain tamponade: a review of decompressive craniectomy management. Neurocrit Care 2008; 9(2): Audrey G. Sinclair, Daniel J. Scoffings. Imaging of the Post-operative Cranium. RadioGraphics 2010; 30: Stephanie Lescher, Sonja Schniewindt, Cand. Alina Jurcoane, Christian Senft, and Elke Hattingen. Time window for postoperative reactive enhancement after resection of brain tumors: less than 72 hours. Neurosurg Focus 2014; 37 (6):E3, 6. Jonathan Loree, Vivek Mehta, and Ravi Bhargava. Cranial magnetic resonance imaging findings of leptomeningeal contrast enhancement after pediatric posterior fossa tumor resection and its significance. Neurosurg Pediatrics 2010; 6: ,. 7. Caird JD, Choudhari KA. 'Plunging' during burr hole craniostomy: a persistent problem amongst neurosurgeons in Britain and Ireland. Br J Neurosurg 2003; 17(6): Elster AD, DiPersio DA. Cranial postoperative site: assessment with contrast-enhanced MR imaging. Radiology 1990; 174(1): Farrell CJ, Hoh BL, Pisculli ML, Henson JW, Barker FG 2nd, Curry WT Jr. Limitations of diffusion-weighted imaging in the diagnosis of postoperative infections. Neurosurgery 2008; 62(3): Schirmer CM, Hoit DA, Malek AM. Decompressive hemicraniectomy for the treatment of intractable intracranial hypertension after aneurysmal subarachnoid hemorrhage. Stroke 2007; 38(3): Page 17 of 18

18 11. Yang XF, Wen L, Shen F, et al. Surgical complications secondary to decompressive craniectomy in patients with a head injury: a series of 108 consecutive cases. Acta Neurochir (Wien) 2008; 150(12): Page 18 of 18