10 Suprahyoid and Infrahyoid Neck point ofcontact betweenthespaceandskull base.Space critical structures(cranialnerves, arteries,veins)areatthe consideration istoexamineeach spacealonetoseewhat relationships withtheskullbase, perhapsthemostimportant neck. Whenonethinksaboutthe SHNspacesandtheir interactions withtheskullbase, oralcavity,andinfrahyoid Important SHNspaceanatomicrelationships includetheir CS, RPS,andPVS. including thevisceralspace(VS),posteriorcervical(PCS), inferiorly intothemediastinumorsuperiorlySHN, predominantly belowthehyoidbonewithsomecontinuing perivertebral (PVS)space.TheIHNsofttissuespacesare retropharyngeal space(RPS),danger(DS),and space (MS),parotid(PS),carotid(CS), space (PPS),pharyngealmucosal(PMS),masticator spaces abovethehyoidbone,includingparapharyngeal definitions areneeded.TheSHNisdefinedasdeepfacial In discussingtheextracranialH&Nsofttissues,afew Imaging Anatomy intratonsillar abscessascausesofinfection. odontogenic infections,mandibleosteomyelitis,and from abscess.CTcanalsoidentifysalivaryglandductalcalculi, the bestexam.CECTcanreadilydifferentiateinflammation When thetypeandcauseofH&Ninfectionaresought,CECTis or intracranialinvasionisneeded. specific delineationofexacttumorextent,perineuralspread, desirable examinthissetting.Instead,MRisbestusedwhen times andsusceptibilitytomotionartifactmakeitaless requiring imagingfromtheskullbasetoclavicles.MR CECT, asboththeprimarytumorandnodesmustbeimaged, Squamous cellcarcinoma(SCCa)stagingisbeststartedwith with CECTfromskullbasetotheclavicles. may becausingthepatient'ssymptoms,isbestcompleted Exploratory imaging,animagingsearchforanylesionthat comprise 3commonreasonsimagingisorderedinthisarea. Exploratory imaging,tumorstaging,andabscesssearch Many indicationsexistforimagingtheextracranialH&N. with biopsyareoftenbestdonebyultrasonography. thyroid disease,pediatricnecklesions,andnodalevaluation High-resolution ultrasoundalsohasarole.Superficiallesions, unaffected bymovement. reformations nowpermitsexquisiteimagesoftheIHN degraded asaresult.MultisliceCTwithmultiplanar a "movingtarget"fortheimager.MRimagequalityisoften imaged. Swallowing,coughing,andbreathingmakesthisarea CECT isthemodalityofchoicewhenIHNandmediastinumare precise mappingofSHNlesions. with CTofthefacialbonesandskullbase,acliniciancanobtain spread, anddural/intracranialspread.WhenMRiscombined in definingsofttissueextentoftumor,perineuraltumor and coronalT1fat-saturatedenhancedMRissuperiortoCECT quality isnotdegradedbymovementseenintheIHN.Axial with theinfrahyoidneck(IHN);therefore,MRimage artifact. TheSHNtissueislessaffectedbymotioncompared (SHN) becauseitislessaffectedbyoralcavitydentalamalgam extracranial H&N.MRismostusefulinthesuprahyoidneck Neither CTnorMRisaperfectmodalityforimagingthe Imaging Approaches&Indications Suprahyoid andInfrahyoidNeckOverview extension belowareapparent. by space,theskullbaseinteractionsaboveandIHN fascia. Thefollowing isapracticaldistillatemeant tosimplify Many nomenclatures havebeenusedtodescribe theneck caring forpatientswithdisease inthisarea. understanding ofthesefasciae be graspedbyanyclinician space-specific DDxlists.Itisimperative thataclear very spacesweusetosubdivide neckdiseasesandconstruct can bechallenging.However,it isthesefasciaethatdefinethe Understanding thedeepcervicalfasciae(DCF) oftheneck paraspinal components. The PVSisdividedbyfascialslipintoprevertebraland PVS canbedefinedfromskullbaseabovetoclaviclebelow. purposes, RPSandDScanbeconsideredasingleentity.The continues beyondT3levelintomediastinum.Forimaging IHN toT3level.TheDSisimmediatelyposteriortheRPSbut RPS beginsattheventralclivussuperiorlyandtraversesSHN- and carotidcanalextendsinferiorlytotheaorticarch.The space, however.TheCSbeginsatthefloorofjugularforamen and endsinferiorlyattheclavicle.ItispredominantlyanIHN mediastinum. ThePCSextendssuperiorlytothemastoidtip component, insteadprojectingonlyinferiorlyintothesuperior superior andinferiorprojections.TheVShasnoSHN The IHNspaceanatomicrelationshipsaredefinedbytheir displacement pattern. Larger massesdefinetheirspaceoforiginbasedonthis mass enlargesinoneofthesespaces,itdisplacesthePPSfat. SHN surroundedbythePMS,MS,PS,CS,andRPS.Whena masses. ThePPSsareapairoffat-filledspacesinthelateral SHN spacestothefat-filledPPSsarekeyanalyzing In additiontoskullbaseinteractions,therelationshipsof • • • • • • • • • • • • to emptyintoDSatT3level involvement ofcriticalstructures;itcontinuesinferiorly RPS contactsskullbasealonglowerclivuswithout poststyloid parapharyngealspace CS canbefollowedinferiorlytoaorticarch;alsocalled canal (CNXII),andpetrousinternalcarotidarterycanal; CS meetsjugularforamen(CNIX-XI)floor,hypoglossal extends inferiorlyintoposteriorSMS including stylomastoidforamen(CNVII);parotidtail PS abutsfloorofexternalauditorycanal,mastoidtip, artery); MSendsatinferiorsurfaceofbodymandible (CNV3), andforamenspinosum(middlemeningeal arch, condylarfossa,skullbase,includingforamenovale MS superiorskullbaseinteractionincludeszygomatic mucosal surfaces nasopharyngeal, oropharyngeal,andhypopharyngeal basiocciput, includingforamenlacerum;PMSincludes PMS touchesposteriorbasisphenoidandanterior submandibular space(SMS) critical forameninvolved;itemptiesinferiorlyinto PPS hasblandtriangularskullbaseabutmentwithout PPS anterolaterally More posteromediallateralRPSnodalmassdisplaces anteriorly Posterolateral CSmassdisplacesstyloidprocessandPPS Lateral PSmassdisplacesPPSmedially More anteriorMSmassdisplacesPPSposteriorly Medial PMSmassdisplacesPPSlaterally thorax foramen magnum;PVScontinuesinferiorlytolevelinto PVS toucheslowclivus,encirclesoccipitalcondylesand Suprahyoid and Infrahyoid Neck 11 Pharyngeal SCCa nodal metastasis (VA-VB) Pharyngeal NHL nodal disease nodes Differentiated thyroid carcinoma Differentiated thyroid carcinoma Anaplastic thyroid carcinoma Thyroid NHL Cervical esophageal carcinoma Parathyroid adenoma Posterior cervical space Visceral space houses common carotid artery, internal jugular vein, CS houses common carotid artery, internal jugular and CNX IHN RPS has no nodes and contains only fat Prevertebral PVS has brachial plexus and phrenic nerve, and vertebral body, veins, arteries, and prevertebral only scalene muscles within; paraspinal PVS contains muscles posterior vertebra elements and paraspinal VS contains thyroid and parathyroid glands, trachea, pretracheal esophagus, recurrent laryngeal nerves, and and paratracheal nodes PCS has fat, CNXI, and level V nodes inside Harnsberger HR et al: Differential diagnosis of head and neck lesions based on their space of origin. 1. the suprahyoid part of the neck. AJR Am J Roentgenol. 157(1):147-54, 1991 Smoker WR et al: Differential diagnosis of head and neck lesions based on their space of origin. 2. the infrahyoid portion of the neck. AJR Am J Roentgenol. 157(1):155-9, 1991 • • • • • PVMs are lifted anteriorly or invaded from posterior to anterior. Since most PVS lesions arise from vertebral body, vertebral body destruction and epidural disease will be linked. The DL-DCF "forces" PVS disease into the epidural space. Selected References 1. 2. Approaches to Imaging Issues in SHN and IHN Approaches to Imaging Issues in of analysis when a It is crucial that the clinician has a method evaluation mass is found in the neck. In the SHN, mass (PMS, methodology begins with defining mass space of origin simple, as the mass MS, PS, CS, lateral RPS). When small, this is larger masses, ask, is seen within the confines of one space. In utilize a space- "How does the mass displace the PPS?" Next, specific DDx list. Match the imaging findings to the diagnoses within this list to narrow your differential. With IHN masses, a similar evaluation methodology can be employed. First, determine what space the mass originates in (VS, CS, PCS). Then, review space-specific DDx list. Match radiologic findings of your case to this DDx list. The clinical findings will guide a clinician's differential. Lesions of posterior midline spaces (RPS and PVS) of the neck need different image evaluation. When a lesion is defined here, 1st ask, "How does mass displace prevertebral muscles (PVM)?" In the case of an RPS mass, PVMs are flattened posteriorly or invaded from anterior to posterior. Contrast this imaging appearance to that of the PVS mass in which the The critical contents of IHN spaces are defined next. Warthin tumor paraganglioma Glomus vagale Carotid body paraganglioma Schwannoma of CNIX-XII SCCa nodal metastasis NHL nodal disease metastasis Vertebral body systemic Brachial plexus schwannoma Carotid space Retropharyngeal space Perivertebral space Suprahyoid and Infrahyoid Neck Overview Neck Infrahyoid and Suprahyoid RPS has fat and medial and lateral RPS nodes inside Prevertebral PVS contains vertebral body, veins and arteries, and prevertebral muscles (longus colli and capitis); in paraspinal PVS resides posterior elements of vertebra and paraspinal muscles MS includes posterior mandibular body and ramus, TMJ, CNV3, masseter, medial and lateral pterygoid and temporalis muscles, and pterygoid venous plexus PS contains parotid, extracranial CNVII, nodes, retromandibular vein, and external carotid artery CS contains CNIX-XII, internal jugular vein, and internal carotid artery PPS contains fat with rare minor salivary glands PMS contains mucosa, lymphatic ring, and minor salivary glands; in nasopharyngeal mucosal space, opening of eustachian tube, torus tubarius, adenoids, superior constrictor, and levator palatini muscles can be seen; oropharyngeal mucosal space contains anterior and posterior tonsillar pillars, palatine, and lingual tonsils Malignant nodal metastases Benign mixed tumor Sarcoma Perineural CNV3 SCCa Mucoepidermoid carcinoma Adenoid cystic carcinoma Pharyngeal SCCa Pharyngeal Tonsillar NHL • • • • • • • Common Benign and Malignant Tumors in Spaces of Neck in Spaces Malignant Tumors Benign and Common SCCa = squamous cell carcinoma; NHL = non-Hodgkin lymphoma. SCCa = squamous cell carcinoma; Parotid space Masticator space Pharyngeal mucosal space Pharyngeal most part responsible for the diseases there. Let us begin by most part responsible for the diseases there. defining the critical contents of the SHN spaces. as well as the posterior wall to RPS, separating RPS from DS. as well as the posterior wall to RPS, separating the SL and ML-DCF. DL-DCF contributes to carotid sheath, like neck are for the The internal structures of the spaces of the PVS. A slip of In both the SHN and IHN, the DL-DCF surrounds dividing PVS DL-DCF dives medially to the transverse process, Another slip of into prevertebral and paraspinal components. wall to RPS and DS, DL-DCF, the alar fascia, provides the lateral in the SHN defines the deep margin of the PMS. The ML-DCF in the SHN defines the deep margin of the SHN and IHN. In It contributes to carotid sheath in both the the IHN, it also circumscribes the VS. trapezius muscles, which are derived from the same trapezius muscles, which are derived from carotid sheath of embryologic origin. It also contributes to the the CS in the IHN. (DL-DCF) are the 3 important fascia in the neck. and PS and In the SHN, the SL-DCF circumscribes MS it "invests" neck contributes to the carotid sheath. In the IHN, and by surrounding the infrahyoid strap, sternocleidomastoid, this challenging subject. There are 3main DCF in the neck. The this challenging subject. There are 3main DCF The superficial layer same names are used in the SHN and IHN. (SL-DCF), the middle layer (ML-DCF), and deep layer of DCF 12 Suprahyoid and Infrahyoid Neck Perivertebral space,paraspinal Superficial layer,deepcervical Buccal space,retromaxillary Middle layer,deepcervical Deep layer,deepcervical Lateral pterygoidmuscle prevertebral component prevertebral muscles andthepharyngealmucosal surface. surrounding thePPS: ThePMS,MS,PS,andCS.Notice theretropharyngealfatstripe isnotseeninthehighnasopharynx betweenthe cervical fasciaoutline thespaces.(Bottom)AxialCECTat levelofthenasopharyngealsuprahyoid neckshowsthe4keyspaces PPS anteriorlywithout liftingstyloidprocess.The superficial (yellowline),middle(pink line),anddeep(turquoiseline) layersofdeep mass pushesthePPSposteriorly,a PSmasspushesthePPSmedially,andaCSanteriorly. LateralRPSmasspushes Retropharyngeal (RPS)andperivertebral spaces(PVS)arethemidlinenonpairedspaces.APMSmass pushesthePPSlaterally,anMS critical pairedspacesofthisregion, thepharyngealmucosal(PMS),masticator(MS),parotid(PS),and carotidspaces(CS). (Top) Axialgraphicdepictsthespacesof thesuprahyoidneck.Surroundingpairedfat-filledparapharyngeal spaces(PPS)arethe4 Retropharyngeal space Internal carotidartery Internal jugularvein Perivertebral space, Temporalis muscle Masseter muscle Styloid process component fat pad fascia fascia fascia Suprahyoid andInfrahyoidNeckOverview Carotid space Parotid space Parapharyngeal space space/surface Pharyngeal mucosal Masticator space Carotid space Parotid space Parapharyngeal space Masticator space space) Retromaxillary fatpad(buccal space/surface Pharyngeal mucosal Suprahyoid and Infrahyoid Neck 13 Retropharyngeal/danger space Jugulodigastric node Parotid space (tail) Prevertebral component, perivertebral space Posterior cervical space Perivertebral space Paraspinal component, perivertebral space Middle layer, deep cervical fascia Masticator space Posterior belly, digastric muscle Parapharyngeal space Parotid space Carotid space Posterior cervical space Suprahyoid and Infrahyoid Neck Overview Neck Infrahyoid and Suprahyoid fascia fascia Alar fascia component Danger space space/surface Platysma muscle Trapezius muscle Perivertebral space, Pharyngeal mucosal Submandibular gland Submandibular space Retropharyngeal space prevertebral component Deep layer, deep cervical Pharyngeal mucosal space Sternocleidomastoid muscle Superficial layer, deep cervical Superficial layer, deep Perivertebral space, paraspinal that makes up the lateral borders of the RPS is not shown. deep (turquoise line) layers of deep cervical fascia outline the suprahyoid neck spaces. Notice the lateral borders of the RPS and danger deep (turquoise line) layers of deep cervical fascia outline the suprahyoid neck spaces. Notice fascia. The CS has a tricolored fascial spaces are called the alar fascia, which represents a slip of the deep layer of deep cervical to the carotid sheath. (Bottom) In representation for the carotid sheath. This is because all 3 layers of deep cervical fascia contribute between them is the RPS. The alar fascia this image, through the low oropharynx, the PMS and the PVS have been outlined. The space Axial graphic shows the suprahyoid neck spaces at the level of the oropharynx. The superficial (yellow line), middle (pink line), and (Top) Axial graphic shows the suprahyoid neck spaces at the level of the oropharynx. The superficial 14 Suprahyoid and Infrahyoid Neck Perivertebral space,paraspinal Sternocleidomastoid muscle fascia touchestransverse Deep layer,deepcervical prevertebral component Levator scapulaemuscle space, whiletheRPS andPVSareposterior. space containsthe high-densitythyroidgland,the upper cervicalesophagus,andthe cricoidcartilage.TheCSarelateral tothevisceral (Bottom) InthisaxialCECT, themiddlelayerofdeepcervical fasciaisdrawntodelineatethe margins ofthevisceralspace.The visceral middle layer(pinkline)circumscribes thevisceralspace,whilesuperficiallayer(yellowline)"invests" theneckdeeptissues. deep layer(turquoiseline)completely circlesthePVS,divinginlaterallytodivideitintoprevertebral andparaspinalcomponents.The suprahyoid andinfrahyoidneck.The carotidsheathismadeupofall3layersdeepcervicalfascia(tricolor linearoundCS).Noticethe (Top) Axialgraphicdepictsthefasciaand spacesoftheinfrahyoidneck.The3layersdeepcervicalfascia arepresentinthe Anterior scalenemuscle Retropharyngeal space Anterior cervicalspace Middle scalenemuscle External jugularvein Perivertebral space, Trapezius muscle Platysma muscle Cricoid cartilage Danger space component Esophagus process Suprahyoid andInfrahyoidNeckOverview fascia Deep layer,deepcervical Posterior cervicalspace fascia Superficial layer,deepcervical Carotid space Carotid sheath Visceral space fascia Middle layer,deepcervical perivertebral space Paraspinal component, Posterior cervicalspace perivertebral space Prevertebral component, Carotid space Visceral space Thyroid gland Anterior cervicalspace Suprahyoid and Infrahyoid Neck 15 Deep layer, deep cervical fascia Retropharyngeal space Danger space Perivertebral space, paraspinal component Perivertebral space, prevertebral component T3 vertebral body Fascial "trap door" Suprazygomatic masticator space CNV3 in foramen ovale Anterior parotid space Parapharyngeal space Infrazygomatic masticator space Superficial layer, deep cervical fascia Submandibular space Suprahyoid and Infrahyoid Neck Overview Neck Infrahyoid and Suprahyoid space fascia fascia fascia Trachea Esophagus Hyoid bone Basisphenoid Visceral space Zygomatic arch Sublingual space Foramen lacerum Submandibular space internal carotid artery Nasopharyngeal mucosal Anteromedial tip, petrous Middle layer, deep cervical Middle layer, deep cervical Oropharyngeal mucosal space Superficial layer, deep cervical approximate level of T3 vertebral body that serves as a conduit from the RPS to the danger space. RPS infection or tumor may access approximate level of T3 vertebral body that serves as a conduit from the RPS to the danger the mediastinum via this route of spread. the skull base, including CNV3. The PMS abuts the basisphenoid and foramen lacerum. The foramen lacerum is the cartilage-covered the skull base, including CNV3. The PMS abuts the basisphenoid and foramen lacerum. The floor of the anteromedial petrous internal carotid artery canal. (Bottom) Sagittal graphic depicts longitudinal spatial relationships of cervical fascia (pink line). Just anterior to the infrahyoid neck. Anteriorly, the visceral space is seen surrounded by middle layer of deep the fascial "trap door" found at the the vertebral column, the RPS and danger space run inferiorly toward the mediastinum. Notice Coronal graphic shows suprahyoid neck spaces as they interact with the skull base. The MS has the largest area of abutment with (Top) Coronal graphic shows suprahyoid neck spaces as they interact with the skull base. The MS