1	‘Doctor ! What is this bump on my head?’ Evaluation of Lesions Presenting in the Scalp and Calvarium Gabriel Pivawer, DO¹; Zafar Bajwa, MD¹; Deborah L. Reede, MD¹; Wendy R.K. Smoker, MD²; Lindell Gentry MD³; Roy A. Holliday, MD⁴
2	Table of Contents Introduction Objectives Gross anatomy Layers of the scalp Vascular supply - Arterial and Venous Innervation - Sensory and Motor Lymphatic drainage
3	Introduction A recent article by L.A. Hyman^* reviewed the five anatomic layers of the scalp and described three layers that are discernable using cross-sectional imaging. This sparked our interest to analyze patients who present with focal or diffuse bumps on the head. We reviewed 75 cases that presented at four major teaching institutions over a two-year period. These cases were analyzed with regards to location and imaging characteristics.
4	Objectives Review the gross anatomy of the scalp and calvarium Demonstrate lesions encountered in each of the radiographically discernible layers of the scalp and calvarium Learn pertinent anatomic considerations for predicting disease spread and surgical planning
5	Layers of the SCALP Skin Connective Tissue (Subcutaneous) Aponeurotica (Galea) Loose connective tissue (Subgaleal) Periosteum (Pericranium) Bone
6	Layer 1 - Skin Consist of the epidermis, dermis and hypodermis Contains hair follicles, sweat glands, sebaceous glands, arteries, and veins Normally 3 to 8 mm thick
7	Layer 2 - Connective Tissue Fibrofatty layer of dense fibrous connective and adipose tissue Contains arteries, veins, lymphatics and cutaneous nerves Skin lacerations extending into this layer bleed profusely because the dense connective tissue does not retract
8	Layer 3 – Aponeurotica (Galea) Thin tendinous structure that bridges the paired occipital and frontal bellies of the occipitofrontalis muscle Continues laterally as the temporal fascia Normally 1-2 mm thick
9	Layer 4 - Loose Connective Tissue (Subgaleal) Loose fibroareolar tissue Predominately avascular Plane for scalp flaps for craniofacial and neurosurgical procedures Danger Space
10	Layer 4 - Loose Connective Tissue (Subgaleal) This is also called the Danger Space. The frontalis muscle inserts into the skin and subcutaneous tissue not bone. This facilitates the spread of disease (blood, tumor and infection) from this layer into the upper, and occasionally the lower, eye lid. Emissary veins traverse this layer and pass through skull foramina, allowing for spread of infection and tumor into the intracranial compartment.
11	Layer 5- Periosteum Periosteum of the skull Continuous with the endosteum at the suture lines Potential space where fluid may loculate Subperiosteal plane used by some plastic surgeons to avoid injury to the supraorbital nerve dermatome.
12	Vascular Supply – Arterial The supratrochlear and supraorbital arteries, branches of the ophthalmic artery, supply the anterior scalp.
13	Vascular Supply – Arterial Superficial temporal artery supplies the lateral scalp Posterior auricular artery supplies the scalp above and posterior to the ear Occipital artery supplies the posterior scalp
14	Vascular Supply - Venous Draining veins follow similar pathways as their accompanying arteries Emissary veins enter the diploic space from the loose connective tissue layer
15	Innervation - Sensory V1 - Supratrochlear and supraorbital nerves supplies the medial aspect of the lid and forehead V2 - Zygomaticotemporal nerve supplies the anterior temple V3 - Auriculotemporal nerve supplies the temporal region
16	Innervation - Sensory C2 /C3 ventral rami - Lesser occipital nerve supplies the scalp over the lateral occipital region C2 dorsal rami - Greater occipital nerve supplies the medial occipital region to the vertex C3 dorsal rami - 3^rd occipital nerve supplies the lower posterior scalp
17	Innervation - Motor Temporal branch innervates the frontal belly of the occipitofrontalis and temporoparietalis muscles Posterior auricular branch innervates the occipital belly of the occipitofrontalis muscle
18	Lymphatics Located primarily in the connective tissue layer (second layer) Lymphatic vessels do not cross the midline Drain to the extraglandular parotid nodes (preauricular, infra-auricular and posterior auricular), superficial occipital and deep lateral cervical (internal jugular and spinal accessory) nodes
19	Lymphatic Drainage - Patterns Frontal zone - preauricular nodes Parietal zone - postauricular lymph ,infra-auricular parotid or directly into the internal jugular nodes Occipital zone - superficial occipital or directly into the deep lateral neck or deep occipital nodes
20	Imaging Anatomy Radiologically distinguishable layers: Skin Subcutaneous Layer Galea/subgaleal/periosteum (GSP) complex Bone
21	Imaging – Skin Layer
22	Imaging – Subcutaneous Layer
23	Imaging: Galea/subgaleal/periosteum (GSP) Complex Layer
24	Imaging: Galea/subgaleal/periosteum (GSP) Complex Layer
25	Imaging: Bone
26	Cases Based on Imaging Layers of Origin Skin Subcutaneous Layer Galea/subgaleal/periosteum complex (GSP) Bone
27	Skin – Cases Skin cancer – squamous and basal cell Kaposi Sarcoma Sebaceous cyst Skin tags Skin calcifications
28	Skin Carcinoma Basal cell, squamous cell, melanoma and Kaposi sarcoma Basal cell is the most common People with fair hair, blue eyes and light skin are at risk Ultraviolet light exposure is the overwhelming cause Exposure to arsenic, hydrocarbons in tar, oils and soot may increase risk of squamous cell carcinoma
29	Skin Cancer
30	Kaposi Sarcoma
31	Sebaceous cyst Eponyms - epidermal cyst, keratin cyst, epidermoid cyst Movable masses under the skin surface Usually develops when a swollen hair follicle obstructs the sebaceous gland Commonly found in the head, neck and trunk Typically low density on CT
32	Sebaceous cyst
33	Skin Tag Common benign fleshy papules that occur in skin folds More common in women Uncommon under the age of thirty
34	Skin Calcifications Usually secondary to sever acne
35	Subcutaneous Layer – Cases Lipoma Hemangioma
36	Lipoma Encapsulated fatty mass Can occur anywhere in the head and neck If there are thick septations or areas of soft tissue density, exclusion of liposarcoma is necessary
37	Lipoma
38	Lipoma
39	Hemangioma Most common tumor of the head and neck in infancy and childhood Present in the first month of life Term used to describe lesions that present in early infancy, rapidly enlarge and involute before adolescence
40	Hemangioma
41	Galea/subgaleal/periosteum complex (GSP) Lesions Cephalohematoma Dermoids Plexiform neurofibroma
42	Cephalohematoma Traumatic subperiosteal accumulation of blood confined by the cranial sutures Usually found over the parietal bone Tend to increase in size after birth and present as a tense firm mass Resolve in weeks to months CT/MRI – Crescent shaped lesions adjacent to the outer table of the skull Chronic cephalohematomas may be hyperdense or calcified MRI – Signal intensity of subacute hemorrhage
43	Cephalohematoma
44	Dermoids Result of persistence of ectodermal elements at the sites of closure (sutures, neural tube, and diverticulation of cerebral hemispheres) Dermoids – contain ectoderm and skin Common locations – midline>frontotemporal> parietal location Dermoids may be associated with external skin ostia or deep sinus tract CT – fat attenuation MRI - Dermoids – hyperintense on T1WI, hypointense on T2WI
45	Dermoid
46	Plexiform Neurofibroma Locally aggressive congenital lesions that progress along the nerve of origin into the intracranial space, most commonly the orbit Typically found in patients with NF-1 Heterogenous on MRI and low attenuation on CT Demonstrate contrast enhancement
47	Plexiform neurofibroma
48	Bone – Cases Intraosseous Epidermoid Intraosseous Hemangioma Intraosseous Meningioma Fibrous dysplasia Paget’s disease ( +/- osteogenic sarcoma) Osteoma Solitary Plasmacytoma Metastatic disease Osteomyelitis
49	Intraosseous Epidermoid 90% intradural, primarily in basal cisterns 10% extradural, primarily in the skull and spine Contain ectoderm (no skin) CT – fluid attenuation MRI – hypointense on T1WI and hyperintense on T2WI Bright on diffusion weighted images
50	Intraosseous Epidermoid
51	Intraosseous Hemangioma Benign lesions Occur in all age groups - F:M = 3:1 Common in the frontal and parietal bones X-ray – Coarse honeycomb or sunburst trabecular pattern CT – Outer table is involved with preservation of the inner table Inhomogeneous contrast enhancement
52	Hemangioma MRI – Hyperintense on TIWI and heterogenously hyperintense on T2WI with hypointense borders Flow voids seen on both T1 and T2 sequences
53	Hemangioma
54	Intraosseous Meningioma Expands the inner and outer tables of the calvarium There may be no dural component May extend into the scalp
55	Intraosseous Meningioma
56	Meningioma
57	Fibrous Dysplasia Commonly affects adolescents and young adults Monostotic and polyostotic forms Replacement of the medullary cavity with fibro-cellular tissue resulting in expansion of the diploic space Outer table tends to bulge more than the inner table Variable enhancement Radionuclide bone scan can be used to exclude polyostotic disease
58	Fibrous Dysplasia Three radiographic patterns: Predominately sclerotic (38%) Predominately lytic (22%) Mixed pattern (40%) Involves both inner and outer tables Often has “ground glass” appearance Asymmetric involvement of the cranium – 10% of monostotic and 50% of polystotic cases
59	Fibrous Dysplasia
60	Paget’s Disease Chronic progressive disease with initial destruction of bone followed by a reparative process Usually affects older patients Usually polystotic (can affect any bone) Three stages of disease in the skull: Vascular – enlargement of skull Advancing sclerosis – thickening of the cortex Complete diffuse sclerosis – loss of distinction between the diploic space and calvarium
61	Paget’s Disease X-ray patterns - osteolytic, osteosclerotic, or mixed “Cotton ball” – round areas of sclerosis with surrounding demineralization Symmetric involvement of the cranium CT – diploic widening and thickened cortex
62	Paget’s
63	Paget’s Sarcoma 1% of patients with Paget’s disease will develop osteosarcoma More common with polyostotic Paget’s - worse prognosis Common sites - femur, humerus, pelvis, skull and tibia. X-ray: ill-defined, primarily osteolytic lesion of the medullary cavity, with aggressive cortical destruction and extension into the soft tissues
64	Paget’s Sarcoma CT: Useful to detect early signs of sarcomatous degeneration (destruction of the cortex and formation of soft tissue mass) MRI: Also used to detect soft tissue components and to evaluate for skip lesions in the medullary cavity CT and MRI are equally sensitive for assessing tumor spread
65	Paget’s Sarcoma
66	Osteoma Mass composed of dense bone formed in the periosteum Arise from membranous bones - common in skull and facial bone Three different histological subtypes: Compact type – arise from outer table ( most common) Cancellous and fibrous – associated with inner table
67	Osteoma X-ray: Dense homogenous bone that protrudes into a sinus or away from the bone CT: Well-defined calcified lesion extending away from the bone with no effect on the adjacent marrow (diploic space) MRI: Low on T1W images and variable signal intensity on T2W images
68	Osteoma
69	Osteoma
70	Plasmacytoma Solitary plasmacytomas of the skull are rare X-ray: Lytic lesions with sharp borders, lack of bony sclerosis and paucity of periosteal reaction CT Osteolytic lesion without sclerotic rim Hyperdense tumor with homogenous enhancement MRI Variable intensity on T1WI Homogenous enhancement
71	Plasmacytoma
72	Metastatic Disease Most commonly breast, prostate, and neuroblastoma Osteoblastic (sclerosis and thickening) Prostate, breast, bladder, hypernephroma Osteoclastic (bone destruction and lucency) Lung, uterus, GI tract, thyroid, melanoma
73	Metastasis - Breast
74	Metastasis - SCCA
75	Lesions involving Bone with Intracranial and /or Extracranial Involvement Sarcomas Lymphoma Infection
76	Rhabdomyosarcoma Most common soft tissue sarcoma in infants and children Third most common primary malignancy of the head and neck Two peaks: 2 - 6 yrs and 14 -18 yrs 40% arise in the head and neck: Orbit, nasopharynx, paranasal sinuses, middle ear, and external auditory canal Often causes extensive local bone destruction Spread intracranially through fissures and skull foramina
77	Rhabdomyosarcoma
78	Ewing’s Sarcoma Rare malignant tumor of bone – 5% of bone tumors Commonly involves long bones, pelvis, and ribs Primary Ewing’s sarcoma of skull is very rare X- Ray: Permeative pattern of bone destruction with a large soft tissue mass Onion skin appearance with laminated periosteal changes MRI: Non-specific findings
79	Ewing’s Sarcoma
80	B-Cell Lymphoma 80%-90% of non-Hodgkin lymphoma Usually originates in the lymphoid tissue and can spread to other organs Older patients (> 50 yrs) CXR/CT: Initial evaluation to identify both nodal and extra-nodal involvement MRI: Useful in identifying bone and CNS involvement
81	B- Cell Lymphoma
82
83	Coccidioidomycosis Less then 1% of cases result in extrapulmonary or disseminated disease Usually develops within a year after the initial exposure Common sites involved: Skin, soft tissues, bones, joints, and CNS Disseminated: 50% have bone involvement Skull involvement with epidural extension is rare
84	Coccidiomycosis
85	Miscellaneous – Selected Cases Mucocele Pott’s Puffy Tumor Encephalocele Thalassemia
86	Mucocele Occurs when there is obstruction of the sinus ostia Frontal sinuses most commonly involved Expands bone
87	Pott’s Puffy Tumor Subperiosteal abscess of the frontal bone with osteomyelitis Etiology: Trauma and frontal sinusitis Common organisms: Strep, Staph, and anaerobes Usually diagnosed with contrast enhanced CT or MRI MRI: Linear enhancement of the dura, extra-axial fluid collection, or cerebritis TX: Surgical drainage
88	Pott’s Puffy Tumor
89
90	Encephalocele Defect in the skull and dura with extra-cranial extension of intra-cranial structures Most common sites are midline at the occiput, frontoethmoidal, parietal bone and nasopharynx MRI is the imaging study of choice – best for evaluating brain or soft tissue involvement
91	Encephalocele
92	Summary - Anatomy S Skin Contains hair follicles, sebaceous glands, arteries and veins C Connective tissue layer Contains arteries, veins and lymphatics A Aponeurotica Helps limits the spread of infection and tumor from the skin and connective tissue layers to the deeper subgaleal region L Loose connective tissue Relatively avascular layer where flaps for neurosurgical and craniofacial procedures are raised Danger Space - Blood, infection and tumor in this layer can spread to the eye lids P Periosteum Potential space where fluid may loculate. Subperiosteal plane used by plastic surgeons to avoid injury to the supraorbital nerve BONE - Pathology can spread intracranially across foramina and sutures
93	Summary Imaging: Skin and Connective tissue layers S - Skin lesions are typically not imaged unless lesions are large and immobile C - Lipomas and hemangiomas occur primarily in this layer – have characteristic imaging findings
94	Summary Imaging: GSP complex A (galea) L (subgaleal) P (pericranium) - The individual anatomic components of these layers are usually not discernible on cross-sectional imaging. The aponeurosis, however, is often seen when there is pathology in the subgaleal region. Clinical history or findings on physical exam will help make the diagnosis: Cephalohematoma, dermoid, plexiform neurofibroma Lesions involving bone with extracranial and/or intracranial components: Sarcomas, lymphomas, metastatic disease, epidermoids, meningiomas, infection
95	Summary Imaging: Bone Intraosseous lesions: Hemangioma, metastatic disease, osteoma, Paget’s disease, fibrous dysplasia and epidermoid lesions Diffuse bone thickening: Fibrous dysplasia, Paget’s disease, sickle cell anemia, thalassemia, hyperthyroidism, hyperparathyroidism, and dilantin therapy
96	Summary Imaging: Miscellaneous Lesions originating in the frontal sinus: Mucocele, Pott’s puffy tumor Bony defect with cranial contents extending into the scalp: Encephalocele
97
98	References