SSN ANATOMY January 23_ 2000

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SSN ANATOMY January 23_ 2000 Powered By Docstoc
					                                             SSN ANATOMY
                                       Workshop 5: Head & Neck I
                                     Deirdre Kelleher & Magni Hamso

1. What are the layers of the scalp?

                 Composition                      Function                   Clinical
Skin             Greatest concentration of        Outermost protective       Sebaceous Cysts
                 hair & sebaceous glands          layer
Connective       Dense CT, SUPERFICIAL                                       Wounds:
Tissue           vasculature of scalp                                        1. Bleed profusely
                                                                             2. Heal well
                                                                             3. form firm lumps (b/c fluid limited
                                                                             by the density of the CT)
Aponeurosis      4 Muscle Insertions:             Musculotendinous Layer     Deep Transverse Lacerations of this
                 Frontalis, Occipitalis, Ant                                 layer GAPE WIDELY
                 and Superior Auricularis
Loose CT         Rich network of DEEP             Permits movement of the    A. DANGER SPACE*: Extracranial
                 arteries/veins                   scalp                      Hematoma can --
                                                                             1. extend posteriorly  S. nuchal line
                                                                             2. extend anteriorly  black eye
                                                                             3. extend laterally  temporal line

                                                                             B. Scalp Flaps: plane of separation in
                                                                             injury/surgery

Periostium       Fuses firmly with bones of       Limits the subperiosteal
                 the skulll at the suture lines   space

*DANGER SPACE! The deep veins of the subaponeurotic space communicate with the DIPLOIC
veins of the cranium, and the DURAL SINUSes. Not only does the subapo space allow fluid to spread
posteriorly, anteriorly, and laterally, it is also a danger space for the spread of infection to the brain.


Fractures of Cranium may involve SCALP, DURA, CNs, Cerebral Tissue.
        Parietal Bone = Most susceptible
        Fx of Temporal Bone  rapid intracranial hemorrhage (epidural hematoma)
        Bone Fragments  can tear venous sinuses/dura/meningeal vessels, or lacerate brain
        Fx @ base of skull  freq. cross foramina  compromise contained structures (vessels/nerves)




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2. CRANIAL FOSSAE!
Foramen                       Location                               Contents
Olfactory Foramina            Ethmoid Bone                           -   Olfactory N
Foramen Cecum                 Bet Ethmoid and Frontal bones          -   Emissary vein (frontal sinus + nasal
                                                                         cavity  superior sagittal sinus)
Optic Canal                   Sphenoid bone                          -   CN II – optic N
                                                                     -   Opthalmic A
                                                                     -   Central vein of retina
Superior Orbital Fissure      Sphenoid bone                          -   CN III – oculomotor N
                              (bet wings of sphenoid bone into the   -   CN IV – trochlear N
                              orbital cavity)                        -   CN V1 – ophthalmic N
                                                                     -   CN VI – abducens N
                                                                     -   Superior ophthalmic veins

Foramen Rotundum              Sphenoid bone (passes into             -   CN V2 – maxillary N
                              pterygopalantine fossa)
Pterygoid/Vidian Canal        Medial Pterygoid Plate                 -   Vidian N (fused greater superficial +
                                                                         deep petrosal Ns)
Foramen Ovale                 Sphenoid bone (passes into             -   CN V3 – mandibular N
                              infratemporal fossa)                   -   Accessory meningeal A
                                                                     -   Lesser Superficial Petrosal N
                                                                     -   Recurrent Meningeal Branch of CN
                                                                         V
                                                                     -   Emissary vein
Foramen Spinosum*             Sphenoid bone                          -   Middle meningeal A
Foramen Lacerum               Bet. Sphenoid and Temporal b.          -   Internal Carotid artery (runs across,
                              (formed by sup/inf defects in the          not through foramen)
                              carotid canal and covered with layer   -   Greater superficial petrosal N
                              of fibrocartilage/periostium)
Hiatus of Facial Canal        Temporal bone                          -   Greater superficial petrosal N
Internal Auditory Meatus      Temporal bone                          -   CN VII – facial N
                                                                     -   CN VIII – vestibulocochlear N

Stylomastoid Foramen          Bet. Mastoid and Styloid Process       -   CN VII
(end of facial canal)
Jugular foramen               Bet. Temporal and occipial b.          -   CN IX – glossopharyngeal N
                                                                     -   CN X – vagus N
                                                                     -   CN XI – spinal accessory N (returns
                                                                         from C1-C5 via foramen magnum)
                                                                     -   Internal jugular vein
Hypoglossal Canal             Occipital bone                         -   CN XII – hypoglossal N
(Anterior Condylar Canal)
Posterior Condylar Canal      Occipital bone                         -   Emissary Vein (sigmoid sinus 
                                                                         veins of pericranium)
Foramen Magnum                Occipital bone                         -   Brain Stem
                                                                     -   Spinal roots of CN XI
                                                                     -   Vertebral arteries
*Common site of fracture  leads to intracranial hemorrhage (epidural hematoma)




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     3. CSF! Please label the following, and trace the path of CSF through the ventricular system
     and then the path of fluid in the venous system.


     Straight Sinus                        Fourth Ventricle                  Arachnoid Villi
     Superior Sagittal Sinus               Cerebral Aqueduct                 Choroid Plexus
     Transverse Sinus                      Foramen of Monro                  Foramina of Luschka
     Lateral Ventricle                     Foramen of Magendie
     Third Ventricle                       Subarachnoid Space

                       Choroid Plexus              Superior Sagittal Sinus

                                                                                 Arachnoid Villi
 Subarachnoid Space

                                                                                  Straight Sinus




Lateral Ventricle

                               Third                                             Transverse Sinus
Foramen of Monro               ventricle

                               Cerebral                                      Fourth Ventricle
                               aqueduct
                                                                       Foramen of Magendie (Medial)
                                                                       Foramen of Luschka (Lateral)


     VENTRICULAR DRAINAGE:
     2 Lateral ventricles – via foramen of Monro → 3rd ventricle – via cerebral aqueduct → 4th
     ventricle →
             1.) central canal of spinal cord
             2.) via foramen of Magendie/2 foramina of Luschka → cisterna magna → subarachnoid
             space – via arachnoid villa → superior sagittal sinus


     VENOUS DRAINAGE:
     Superior sagittal sinus → right transverse sinus (predominantly)
     Inferior sagittal sinus + cerebral vein → straight sinus + occipital sinus → left transverse sinus
     (predominantly)
     Superior petrosal sinus + transverse sinus → sigmoid sinus → internal jugular vein




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4. HEMATOMAS!

Intracranial Bleeding:
       Elevated intracranial Pressure  space-occupying hematomas  HA, N/V, depressed
          consciousness, edema of optic disk
       Tentorial Herniation  oculomotor nerve compression  loss of papillary constriction
          (ipsilateral followed by bilateral)
       Medullary Herniation  medulla compression (foramen magnum)  anoxia 
          DEATH



                Vessel          Extravasation       Cause            Symptoms                   Correction
Epidural        Middle          Potential Space     Fx of            - HIGH pressure            Emergency
“Talk-and-die   Meningeal       bet two layers of   temporal or      - ARTERIAL bleed           Craniotomy
Syndrome”       Artery          dura mater          parietal bone    - Sx of brain
                                                                     compression (w/in 2-3
                                                                     hrs)
                                                                     - Transient LOC 
                                                                     Lucid Interval  death
Subdural        Veins of        Potential space     Shear force      - LOW pressure
                Arachnoid       bet dura and        due to sudden    - slow VENOUS bleed
                Layer           arachnoid           jarring/blow     - range of sx due to
                                (Subdural Space)    to head          reduced CSF production
                                                                     (asymptomatic 
                                                                     gradually symp.)
                                                                     -range of consciousness
                                                                     (alert  transient LOC)
Subarachnoid    Cerebral        Subarachnoid        Rupture of       - HA                       Surgery 
“Worst          Artery          space on surface    weakened         - N/V                      usually
Headache of                     of brain            artery or        - Blood in CSF on spinal   futile 
Life”                                               Berry’s          tap                        rapidly fatal
                                                    aneurysm                                    condition
                                                    (circle of
                                                    Willis”
Pial/Subpial    Small vessels   Contained by        Blunt trauma     - LOC at time of event
“Punch Drunk    of brain and    pial layer          causing brain    - Afterwards: atrophy,
Boxer”          pia                                 to strike        degeneration, sclerosis,
                                                    cranial          loss of fxn
                                                    surfaces
                                                    Coup: same
                                                    side as trauma
                                                    Countercoup:
                                                    opposite side
                                                    due to brain
                                                    rebound




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