Imaging of head and neck denervation muscular atrophy

Transcription

1 Imaging of head and neck denervation muscular atrophy Poster No.: C-1498 Congress: ECR 2016 Type: Authors: Keywords: DOI: Educational Exhibit S. Petrovic; Nis/RS Neoplasia, Diagnostic procedure, MR, CT, Neuroradiology peripheral nerve, Head and neck /ecr2016/C-1498 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 13

2 Learning objectives The purpose of this educational exhibit is to review the CT and MR imaging characteristic of head and neck denervation muscular atrophy, to evaluate appearance of acute and chronic forms of muscular denervation and to illustrate denervation muscular atrophy caused by lesion of different cranial nerves. Page 2 of 13

3 Background To the exception of I, II and VIII cranial nerves, all other cranial nerves have motor functions, supplying muscles in the head and neck. Therefore, insults to these nerves can be recognized by denervation. To depict denervation changes and their etiology it is mandatory to know cranial nerves anatomy and the muscles innervated by each of these nerves. The main causes of head and neck muscular denervation atrophy are perineural tumoral spread and tumor invasion. In post-treatment setting, besides perineural recurrence, iatrogenic insult related to surgery (tumoral resection, radical neck dissection, cranial nerves injury) or radiation neuropathy should also be considered. Page 3 of 13

4 Findings and procedure details The role of imaging is to depict denervation changes and to establish its cause. MRI is the imaging modality of choice. To depict denervation changes T1W, T2W,STIR, fat suppression and contrast enhanced T1W MR images should be acquired over the region of affected muscle groups. To depict the cause of denervation all segments of CNs should be explore: intracranial segment corresponding to CNs nuclei, cisternal segment, skull base segment through which the nerves exit the intracranial compartment and exocranial segment. CT can demonstrate the chronic denervation while contrast administration is necessary for depicting the cause. Early acute muscular denervation changes manifest on MRI by increase in muscle volume, signal intensity on both STIR and T2W images and contrast enhancement reflecting oedema. Chronic changes can be seen on both imaging modalities; CT demonstrates muscle hypodensity caused by fatty infiltration and MRI shows loss of muscle volume, fatty replacement and involvement of a group of muscles sharing a common innervation. Patterns of denervation can be divided into simple, affecting one single cranial nerve, or complex, affecting several cranial nerves. Different combinations of cranial nerve deficits indicate the lesion to anatomic areas where these cranial nerves lay close together. The oculomotor nerve (III CN) divides into a superior branch supplying the superior rectus and the levator plapebrae complex and an inferior branch which supplies the medial and inferior recti and the inferior oblique muscles. Clinically, patients with proximal oculomotor nerve paralysis present with ptosis and slight inferior and lateral deviation of the globe.chronic denervation changes present with the loss of muscle bulk, best seen on MR imaging. Isolated trochlear nerve palsy (IV CN) is most often due to trauma and only rarely due to neoplasm, such as meningeoma (Fig.1). On imaging asymmetric bulk of the superior oblique muscles maybe depicted on late stages due to atrophy on the affected side (Fig.1). The mandibular division of the trigeminal nerve (V3 CN) provides motor supply to the masticator muscles (medial and lateral pterygoid, masseter and temporalis muscles), anterior belly of digastric, mylohyoid, tensor tympani and tensor veli palatini muscles. In the chronic stage, fatty replacement of the muscle fibres and volume loss become evident on the affected side (Fig.2,3) and the normal side can be mistaken for a mass lesion by inexperienced radiologist. Primary and secondary neoplasms, particularly perineural spread of head and neck malignancies, are among the most common causes of mandibular division of the trigeminal nerve denervation. Page 4 of 13

5 Patients with abducens nerve (VI CN) palsy present with convergent strabismus on the affected side. The imaging demonstrates atrophy of the lateral rectus on the affected side (Fig.4). Due to anatomic course of CN VI across the cavernous sinus, abducens palsy may be the first sign of a mass lesion in this location. The facial nerve (VII CN) motor root innervates the muscles of facial expression, buccinator, platysma, posterior belly of digastric muscle, stylohyoid,occipitalis, and stapedius muscles. Denervation changes in the facial muscles have only been described in the context of facial nerve dysfunction due to malignant infiltration of the parotid (Fig.5) and after skull-base surgery. Because the muscles of facial expression are too small, imaging signs of denervation may only be depicted in a chronic stage when there is loss of muscle bulk leading to asymmetry with the opposite side (Fig.5) The glossopharyngeal nerve (IX CN) supplies innervation to stylopharyngeus muscle and contributes to motor innervation to palatoglossus and palantopharyngeus muscles, superior and middle pharyngeal constrictor muscles and levator veli palatini muscle. Denervation changes of stylopharyngeus muscle are difficult to demonstrate due to the small size of these muscles. The motor fibres of the vagus (X CN) supply the soft palate, constrictor muscles, as well as the intrinsic and extrinsic laryngeal muscles. Dysfunction of the vagus nerve paralyses the larynx and is manifested by a hoarse voice. Acute vagal neuropathy and vocal cord paralysis is often idiopathic whereas chronic dysfunction is usually due to malignancy, surgical injury or idiopathic causes. Distal vagal (or recurrent laryngeal nerve) lesions may be a cause of extrathyroid neck tumours (Fig.6D), thyoid masses or mediastinal masses. The spinal accessory nerve (XI CN) innervates the sternocleidomastoid muscle and the trapezius muscle. The radiological findings of denervation are only described in the later stages where there is atrophy of the ipsilateral trapezius and sternocleidomastoid muscles (Fig.6.D). It is not uncommon to have isolated spinal accessory nerve palsy, most often iatrogenic resulting from neck dissection. In addition CN XI may also be involved by any lesion affecting the jugular foramen (Fig.6) or the cranio-cervical junction. The hypoglossal nerve (XII CN) is almost completely formed by somatic motor fibres. CN XII supplies motor innervation to the intrinsic and extrinsic tongue musculature and the strap muscles.chronic denervation present as atrophy and fatty replacement of the hemitongue (Fig.6C). In the literature describing imaging changes in the denervated tongue, skull-base tumours (meningioma, nasopharyngeal tumour extension, metastasis, sarcoma, chordoma, glomus tumour), hypoglossal nerve schwannoma, surgery, radiotherapy, metastatic nodal disease in the carotid sheath and upper aerodigestive tract or salivary carcinoma are featured. Most patterns of denervation involving the lower cranial nerves are complex, secondary to lesions located in the jugular foramen (Fig.6.) or high in the post-styloid parapharyngeal space and manifest clinically by Vernet's syndrome reflecting the involvement of CNs Page 5 of 13

6 IX-XI. When also affecting CN XII, the resulting clinical picture is named Collet-Sicard syndrome reflecting a complex pattern of denervation atrophy (Fig.6). Most common lesions affecting the entire set of lower cranial nerves include posterior skull base fractures and expansile lesions in the jugular foramen (mostly metastasis, meningiomas, neural sheath tumours and paragangliomas) Page 6 of 13

7 Images for this section: Fig. 1: A) Coronal T2w Flair MR image with fat suppression shows chronic denervation atrophy of the left superior oblique muscle (thick arrow) due to CN IV palsy and B) postcontrast axial T1w MR image, meningeoma (arrow) as a cause of muscular denervation - Nis/RS Fig. 2: Postontrast axial and coronal T1w MR images demostrate: A) trigeminal schwannoma (arrow), B) chronic muscular denervation atrophy of masseter and medial pterygoid muscles (arrows), C) chronic muscular denervation atrophy of temporalis, masseter and anterior belly of digastric muscles (arrows) - Nis/RS Page 7 of 13

8 Fig. 3: Fig.3. Postcontrast axial CT scans demonstrate chronic denervation atrophy of: A) masseter and medial pterygoid muscles (arrows) B) tensor veli palatini muscle on the right side (big arrow) C) anterior belly of digastric muscle ( thick arrows) due to mandibular nerve palsy - Nis/RS Fig. 4: Coronal CT scan demonstrates chronic denervation atrophy of the lateral rectus muscle on the right side ( small arrow) due to CN VI palsy - Nis/RS Page 8 of 13

9 Fig. 5: Axial T2w MR images demonstrate: A) adenoid cystic carcinoma of the right parotid gland (arrow) B) denervation atrophy of the alar nasi and the zygomaticus major muscles due to infiltration of facial nerve (thick arrows) C) axial postcontrast T1w image demonstrate atrophy of buccinator muscle on the right side (thick arrow). - Nis/RS Page 9 of 13

10 Fig. 6: Axial bone window and postcontrast CT scans demonstrate lower CNs palsy due to glomus jugulare paraganglioma A) destruction of the scul base at the level of jugular foramen (arrow) B) jugular paraganglioma after contrast administration (arrow) C) fatty infiltration of the left hemitongue (arrows) due to XII CN palsy D) loss of bulk and fatty replacement of the left vocal cord (thin arrows) and denervation atrophy due to spinal accessory nerve palsy with atrophy of the left sternocleidomastoid and trapezius muscles (thick arrows) - Nis/RS Page 10 of 13

11 Conclusion Muscular denervation atrophy may be the first sign of a cranial nerve pathology. High resolution CT and MR imaging have main role in diagnostics of acute and chronic muscular denervation. To avoid misdiagnosing of denervation for mass lesions it is mandatory to know patterns of these changes. Page 11 of 13

12 Personal information Sladjana Petrovic, M.D., Ph.D. Faculty of Medicine University of Niš Center of Radiology Clinical Centre Niš Blvd. Dr Zorana Djindjica Nis Serbia Page 12 of 13

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