Dominant Left Transverse Sinus Drains Both Superior Headache

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Head and Neck

I. ARTERIAL SUPPLY AND VENOUS DRAINAGE (Figure 20-1)

A. The arch of the aorta (see Figure 3-7) consists of the following branches:

1. Brachiocephalic artery, which branches into:

a. Right subclavian artery b. Right common carotid artery

2. Left common carotid artery

3. Left subclavian artery

B. The external carotid artery has eight branches in the neck. The most important are the superior thyroid, lingual, facial, occipital, maxillary, and superficial tempo-

Figure 20-1. (/\) Arterial supply of the head and neck region. (B) Lateral arteriogram and (C) lat- ► eral arteriogram with digital subtraction. (D) Lateral arteriogram showing a blocked internal carotid artery (arrow). The most common location of atherosclerosis in the carotid artery is at the bifurcation of the common carotid artery. Carotid artery plaques usually are ulcerated. (E) The surgical exposure used in a carotid endarterectomy within the anterior (carotid) triangle of the neck. Note the anatomic structures that may be at risk during this procedure. The incision is made along the anterior border of the sternocleidomastoid muscle, and the facial vein is ligated and cut to better expose the carotid bifurcation. Carotid endarterectomy is performed to remove blockages of the internal carotid artery. This procedure can reduce the risk of stroke in patients who have emboli or plaques that cause transient monocular blindness (amaurosis fugax), which is the classic ocular symptom of a transient ischemic attack. Transient monocular blindness should not be ignored because it indicates the presence of emboli to the central artery of the retina, a terminal branch of the internal carotid artery (internal carotid artery > ophthalmic artery > central artery of the retina). Hollenhorst cholesterol plaques are observed during a retinal examination. Contralateral hemiplegia and hemianesthesia also may occur if blood flow to the middle cerebral artery is insufficient. ANSA = nerves of the ansa cervicalis; C = common carotid artery; CN X= vagus nerve; CN XII = hypoglossal nerve; CSI= carotid sinus; CSY= carotid siphon; EC = external carotid artery; F= facial artery; FV= facial vein (cut); IA = inferior alveolar artery; IC= internal carotid artery; I J V= internal jugular vein; IT= inferior thyroid artery; L = lingual artery; ME = middle meningeal artery; MX = maxillary artery; OC = occipital artery; SPT = superficial temporal artery; ST = superior thyroid artery; STV = superior thyroid vein; VE = vertebral artery. (A adapted with permission from Moore KL: Clinically Oriented Anatomy 3rd ed. Baltimore, Williams & Wilkins, 1992, p 666; B and C adapted with permission from Fleckenstein P, Tranum-Jensen J: Anatomy in Diagnostic Imaging. Philadelphia, WB Saunders, 1993, p 157; D adapted with permission from Freedman M: Clinical Imaging: An Introduction to the Role of Imaging in Clinical Practice. New York, Churchill Livingstone, 1988, p 579; £ adapted with permission from Blackbourne LH, Fleischer KJ: Advanced Surgical Recall. Baltimore, Williams & Wilkins, 1997, p 787.)

Dural Branches Vertebral Artery

rai arteries. The maxillary artery enters the infratemporal fossa by passing posterior to the neck of the mandible and forms two branches:

1. The middle meningeal artery, which supplies the periosteal dura mater in the cranium. Skull fractures in the area of the pterion (junction of the parietal, frontal, temporal, and sphenoid bones) may sever the middle meningeal artery, resulting in an epidural hemorrhage.

2. Inferior alveolar artery

C. The internal carotid artery (Figure 20-2) has no branches in the neck and forms the anterior circulation of the circle of Willis. The internal carotid artery has a number of important branches in the head.

1. The ophthalmic artery enters the orbit with the optic nerve (CN II) and branches into the central artery of the retina. Occlusion causes monocular blindness.

2. The anterior cerebral artery (ACA) supplies the motor cortex and sensory cortex for the leg. Occlusion causes contralateral paralysis and contralateral anesthesia of the leg.

3. Middle cerebral artery (MCA). Occlusion of the main stem of this artery causes contralateral hemiplegia, contralateral hemianesthesia, homonymous hemi-anopia (€€ ), and, if the dominant hemisphere is involved, aphasia.

a. The outer cortical branches supply the motor and sensory cortexes for the face and arm. Occlusion causes contralateral paralysis and contralateral anesthesia of the face and arm.

b. The lenticulostriate arteries (deep branches of the middle cerebral artery, or lateral striate arteries) supply the basal ganglia and the internal capsule. Occlusion causes classic "paralytic stroke," with primarily contralateral hemiplegia as a result of destruction of the descending motor fibers in the posterior limb of the internal capsule. Contralateral hemianesthesia may occur if the ascending sensory thalamocortical fibers in the internal capsule also are destroyed. These arteries are susceptible to hemorrhagic infarction as a result of hypertension or atherosclerotic occlusion. Because the lenticulostriate arteries branch at right angles, it is unlikely that an embolus will lodge in them and cause an embolic infarction.

4. The anterior communicating artery connects the two anterior cerebral arteries. It is the most common site for aneurysms (e.g., congenital berry aneurysm). Rupture of an aneurysm causes subarachnoid hemorrhage and, possibly, bitemporal lower quad-rantanopia (©O because of the close proximity of the anterior communicating artery to the optic chiasm.

5. The posterior communicating artery connects the anterior and posterior circulation of the circle of Willis. It is the second most common site of aneurysm (e.g., congenital berry aneurysm). Rupture of an aneurysm in this area causes subarachnoid hemorrhage and, possibly, oculomotor nerve (CN III) paralysis, characterized by a droopy upper eyelid, an eye that looks down and out, diplopia, a fixed and dilated pupil, and lack of accommodation.

Figure 20-2. (A) Anteroposterior arteriogram (digital subtraction) of the internal carotid artery. (B) ► Lateral arteriogram (digital subtraction) of the internal carotid artery. (C) Anteroposterior arteriogram (digital subtraction) of the vertebral artery. (D) Lateral arteriogram (digital subtraction) of the vertebral artery. Cerebrovascular disorders (strokes) most commonly are cerebral infarcts caused by occlusion of the cerebral vessels by thrombosis or embolism, not by hemorrhage. Strokes are characterized by relatively abrupt onset of a focal neurologic deficit. (£) CT scan showing a large stroke in the area of the left middle cerebral artery, with edema and mass effect. No visible hemorrhage is apparent; most strokes are caused by thrombosis or embolism. In a clinical vignette question, first identify the neurologic deficit of stroke mentioned in the question, then match the deficit to the occluded artery (table), and finally identify the appropriate artery on the arteriogram. 1 = ischemic brain parenchyma; 2 = midline shift to the right; 3 = right frontal horn of the lateral ventricle; ACA = anterior cerebral artery; B = basilar artery; IC = internal carotid artery; LS = lenticulostriate arteries of the middle cerebral artery; MCA = middle cerebral artery (stem and outer cortical branches); ME = middle meningeal artery; MX= maxillary artery; OC = occipital artery; OP = ophthalmic artery; PCA - posterior cerebral artery; PCo = posterior communicating artery; VE = vertebral artery. (A-D adapted with permission from Fleckenstein P, Tranum-Jensen J: Anatomy in Diagnostic Imaging. Philadelphia, WB Saunders, 1993, pp 180-183; E reprinted with permission from Bhushan V, Le T, Amin C: First Aid for the USMLE Step 1: A Student to Student Guide. Stamford, CT, Appleton & Lange, 1999.)

Contralateral hemiplegia, contralateral hemianesthesia, homonymous hemianopia, aphasia

Contralateral paralysis and anesthesia of face and arm

Transient Monocular BlindnessPosterior Cerebral Artery Stroke

Neurologic Deficit of Stroke

Ophthalmic ACA

MCA At the stem

Lenticulostriate

Outer cortical PCA

Occluded Artery

Neurologic Deficit of Stroke

Monocular blindness (transient) Contralateral paralysis and contralateral anesthesia of leg

Contralateral hemiplegia, contralateral hemianesthesia, homonymous hemianopia, aphasia

Classic "paralytic stroke" Contralateral hemiplegia, possible contralateral hemianesthesia

Contralateral paralysis and anesthesia of face and arm

Contralateral sensory loss of all modalities with concomitant severe pain (thalamic syndrome of Dejerine and Roussy) Homonymous hemianopia with macular sparing

Medical Students Stroke Syndromes

D. The vertebral artery passes through the transverse foramina of vertebrae CI—6 and the foramen magnum and forms the posterior circulation of the circle of Willis.

1. The basilar artery is formed by the union of the vertebral arteries. It has a number of branches, including the posterior cerebral artery (PCA).

2. The posterior cerebral artery (PCA) supplies the midbrain, thalamus, and occipital lobe with visual cortex. Occlusion causes contralateral sensory loss of all modalities, with concomitant severe pain (i.e., thalamic syndrome of Dejer-ine and Roussy) as a result of damage to the thalamus. It also causes homonymous hemianopia with macular sparing (CO).

E. Venous drainage

1. Face and scalp a. The facial vein, which has no valves, provides the major venous drainage of the face. It drains into the internal jugular vein. The facial vein makes clinically important connections with the cavernous sinus via the superior and inferior ophthalmic veins and the pterygoid plexus of veins. This connection with the cavernous sinus provides a potential route of infection from the superficial face ("danger zone of the face") to the dural venous sinuses within the cranium.

b. Diploic veins, which have no valves, run within the flat bones of the skull.

c. Emissary veins, which have no valves, form an anastomosis between the superficial veins on the outside of the skull and the dural venous sinuses.

2. Dural venous sinuses, which have no valves, form between the endosteal dura and the meningeal dura and include the following sinuses:

a. The superior sagittal sinus, which is located along the superior aspect of the falx cerebri. Arachnoid granulations, which transmit cerebrospinal fluid from the subarachnoid space to the dural venous sinuses, protrude into its wall.

b. The inferior sagittal sinus, which is located along the inferior aspect (free edge) of the falx cerebri c. The straight sinus, which is formed by the union of the inferior sagittal sinus and the great vein of Galen, which drains venous blood from deep areas of the brain d. The occipital sinus, which is located in the attached border of the tentorium cerebelli e. The confluence of sinuses, which is formed by the union of the superior sagittal, straight, and occipital sinuses f. The transverse sinus, which drains venous blood from the confluence of sinuses to the sigmoid sinus g. The sigmoid sinus, which drains into the internal jugular vein h. Cavernous sinuses

(1) General features. The cavernous sinuses are located on either side of the sphenoid bone. They receive venous blood from the facial vein, superior and inferior ophthalmic veins, pterygoid plexus of veins, central vein of the retina, and each other via the intercavernous sinuses, which pass anterior and posterior to the hypophyseal stalk. They drain venous blood into the superior petrosal sinus ► transverse sinus and inferior petrosal sinus > internal jugular vein. The cavernous sinuses are anatomically related to the internal carotid artery (carotid siphon), postganglionic sympathetic nerves, and CN 111, IV, VI, V,, and V2.

(2) Clinical significance. The cavernous sinuses are the most clinically significant sinuses. In infections of the superficial face (see I E 1 a), thrombophlebitis can result in poor drainage and enlargement involving CN III, IV,

VI, V,, and V2, thereby producing ocular signs. Infections can spread from one side to the other through the intercavernous sinuses. Poor drainage may cause exophthalmus and edema of the eyelids and conjunctiva. Fistulas between the carotid artery and cavernous sinus may cause headache, orbital pain, diplopia, arterialization of the conjunctiva, and ocular bruit. *

F. Clinical consideration. Epidural, subdural, subarachnoid, and extracranial hemorrhages may occur within the head area (Figure 20-3).

II. CERVICAL TRIANGLES OF THE NECK (Figure 20-4)

A. General features. The sternocleidomastoid muscle divides the neck into the anterior triangle and posterior triangle, both of which are further subdivided. The most important subdivision of the anterior triangle is the carotid triangle, whereas the most important subdivision of the posterior triangle is the occipital triangle. The carotid and occipital triangles contain important anatomic structures.

B. Clinical considerations

1. Anterior (carotid) triangle a. The platysma muscle lies in the superficial fascia above the anterior triangle and is innervated by the facial nerve. Accidental damage to the facial nerve during surgery in this area can cause distortion of the shape of the mouth.

b. The carotid pulse is easily palpated at the anterior border of the sternocleidomastoid muscle at the level of the superior border of the thyroid cartilage (C5).

c. Bifurcation of the common carotid artery into the internal and external carotid arteries occurs in the anterior triangle of the neck at the level of C4. The carotid body and carotid sinus are found at the bifurcation. The carotid body is an oxygen chemoreceptor; the carotid sinus is a pressure receptor. Sensory information from both is carried to the central nervous system by CN IX and X.

d. Carotid endarterectomy is performed in the anterior (carotid) triangle.

e. The stellate ganglion is the lowest of the three ganglia of the cervical sympathetic trunk. The term stellate ganglion nerve block is not strictly correct because the anesthetic is injected above the stellate ganglion, with enough anesthetic injected to spread both up and down the cervical sympathetic trunk. The needle is inserted between the trachea medially and between the sternocleidomastoid muscle and the common carotid artery laterally, using the cricoid cartilage (C6) and the transverse process of vertebra C6 as landmarks. A successful block causes vasodilation of the blood vessels of the head, neck, and upper limb. It also causes Horner syndrome, which causes miosis (constriction of the pupil due to paralysis of the dilator pupillae muscle), ptosis (drooping of the eyelid due to paralysis of the superior tarsal muscle), and hemianhydrosis (loss of sweating on one side). A stellate ganglion nerve block is used in Raynaud phenomenon and to relieve vasoconstriction after frostbite or microsurgery of the hand.

2. Posterior (occipital) triangle a. Injury to CN XI within the posterior (occipital) triangle (e.g., from surgery or a penetrating wound) causes paralysis of the trapezius muscle. As a result, abduction of the arm past the horizontal position is compromised.

b. Injury to the trunk of the brachial plexus, which lies in the posterior (occipital) triangle, results in Erb-Duchenne or Klumpke syndrome (see Chapter 18 IV F).

c. Severe hemorrhage of the upper limb may be stopped by applying downward and posterior pressure to compress the subclavian artery against the first rib. The

Occipital Posterior PositionSubarachnoid Hemorrhage Csf

Subarachnoid

Type of Hemorrhage

Injury

Blood Vessel Affected

Blood in

CSF?

Clinical Features

Epidural

Skull fracture near pterion or greater wing of sphenoid

Middle cranial fossa A medical emergency

Middle meningeal artery

CT scan shows lens-shaped (biconvex) hyper-density adjacent to bone; arterial blood located between skull and dura Lucid interval for a few hours followed by death ('talk and die syndrome") May cause a transtentorial herniation, which compresses (1) CN III, causing ipsilateral dilated pupil, and (2) cerebral peduncles, causing contralateral hemiparesis

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