20 NORMAL ELECTRICAL FIRING PATTERNS OF CORTICAL NEURONS AND THE ORIGIN AND SPREAD OF SEIZURES

Neurons and Their Properties



25



Electrode placement and

lead identification



Fp2



Fp1



F8



F7

A1



T3



F3



Fz



C3



Cz C4



P3



Pz



F4



P4



T5

O1



A2

T4



T6



O2



Odd numbers, left side

Even numbers, right side

z locations, midline



Normal sleep



EEG in normal awake person, eyes closed

Fp1–F3

F3–C3



�



Fp2–F4

F4–C4



�

�



Fp1–F7



C4–A2

P3–A1

P4–A2

O1–A1



C4–P4

P4–O2



F4–A2

C3–A1



C3–P3

P3–O1



F3–A1



O2–A2

Sleep spindles



�



Right temporal tumor



Fp1–F7



F7–T3



F7–T3



T3–T5



T3–T5



T5–O1



T5–O1



Fp2–F8



Fp2–F8



F8–T4



F8–T4



T4–T6



T4–T6



Epilepsy



T6–O2



T6–O2

Right temporal � activity



1.21  ELECTROENCEPHALOGRAPHY

EEG permits the recording of the collective electrical activity of the cerebral cortex as a summation of activity measured

as a difference between two recording electrodes. Recording

electrodes (leads) are placed on the scalp on at least 16 standard sites, and recordings of potential differences between key

electrodes are obtained. The principal wave forms recorded in

the EEG are alpha (9 to 10 Hz, occipital location, predominant

activity in adults, awake in resting state with eyes closed); beta

(20 to 25 Hz, frontal and precentral locations, prominent in

wakefulness, seen in light sleep); delta (2 to 2.5 Hz, frontal and

central location, not prominent in wakefulness, �generalized in



Left temporal spikes



deep sleep and coma or toxic states); and theta (5 to 6 Hz,

central location, constant and not prominent when awake

and active, sometimes generalized when drowsy). Electrode

placement is shown in figure B. Examples are provided of a

normal EEG taken when client is awake with eyes closed (C), 

and when sleeping normally (D). Abnormal patterns of activity 

can be seen in the presence of tumors (E) and in seizures (F);

for example, the spike-and-wave appearance in a generalized

tonic-�clonic seizure (generalized fast repetitive spikes and

generalized spikes and slow waves, respectively); and a 3 Hz

spike-�and-wave EEG in the case of an absence seizure).



This page is intentionally left blank



2



SKULL AND MENINGES



2.1



Interior View of the Base of the Adult Skull



2.2



Foramina in the Base of the Adult Skull



2.3



Bony Framework of the Head and Neck



2.4



Schematic of the Meninges and Their Relationships to the Brain and Skull



2.5



Hematomas



27



28



Overview of the Nervous System



Frontal bone

Sulcus of superior sagittal sinus

Frontal crest

Sulcus for anterior meningeal vessels

Foramen cecum

Internal surface of orbital part

Ethmoid bone

Crista galli

Cribriform plate

Sphenoid bone

Lesser wing

Anterior clinoid process

Greater wing

Sulcus for middle meningeal

vessels (frontal branches)

Body

Jugum

Prechiasmatic sulcus

Tuberculum sellae

Sella

Hypophyseal fossa

turcica

Posterior clinoid process

Dorsum sellae

Groove for internal carotid artery

Temporal bone

Squamous part

Petrous part

Sulcus of lesser petrosal nerve

Sulcus of greater petrosal nerve

Cartilage of auditory tube

Arcuate eminence

Sulcus of superior petrosal sinus

Sulcus of sigmoid sinus



Anterior cranial fossa



Middle cranial fossa



Posterior cranial fossa



Parietal bone

Sulcus for middle meningeal

vessels (parietal branches)

Mastoid angle

Occipital bone

Basilar part

Sulcus of inferior petrosal sinus

Sulci for posterior meningeal vessels

Condyle

Sulcus of transverse sinus

Sulcus of occipital sinus

Internal occipital crest

Internal occipital protuberance

Sulcus of superior sagittal sinus



2.1  INTERIOR VIEW OF THE BASE OF THE

ADULT SKULL

The anterior, middle, and posterior cranial fossae house the

anterior frontal lobe, temporal lobe, and cerebellum and

brain stem, respectively. The fossae are separated from each

other by bony structures and dural membranes. A swelling of



the brain or the presence of mass lesions can selectively exert

pressure within an individual fossa. The perforated cribriform

plate allows the olfactory nerves to penetrate into the olfactory

bulb, a site where head trauma can result in the tearing of the

penetrating olfactory nerve fibers.



Skull and Meninges



Foramen cecum



Vein to superior sagittal sinus



Anterior ethmoidal foramen



Anterior ethmoidal artery, vein and nerve



Foramina of cribriform plate



Olfactory nerve bundles



Posterior ethmoidal foramen



Posterior ethmoidal artery, vein and nerve



Optic canal



Optic (II) nerve

Ophthalmic artery



Superior orbital fissure



Oculomotor (III) nerve

Trochlear (IV) nerve

Ophthalmic nerve

Abducens (VI) nerve

Superior ophthalmic vein



Foramen rotundum



Maxillary nerve



Foramen ovale



Mandibular nerve

Accessory meningeal artery

Lesser petrosal nerve

(occasionally)



Foramen spinosum



Middle meningeal artery and vein

Meningeal branch

of mandibular nerve



Foramen of Vesalius

(inconstant)



Small emissary vein



Foramen lacerum



Interior carotid artery

Interior carotid nerve plexus



Hiatus of canal of

Hiatus of canal of



Lesser petrosal nerve

Greater petrosal nerve



Interior acoustic meatus



Facial (VII) nerve

Vestibulocochlear (VIII) nerve

Labyrinthine artery



Vestibular aqueduct



Endolymphatic duct



Mastoid foramen

(inconstant)



Emissary vein

Branch of occipital artery



Jugular foramen



Inferior petrosal sinus

Glossopharyngeal (IX) nerve

Vagus (X) nerve

Accessory (XI) nerve

Sigmoid sinus

Posterior meningeal artery



Condylar canal

(inconstant)



Emissary vein

Meningeal branch of

ascending pharyngeal artery



Hypoglossal canal



Hypoglossal (XII) nerve



Foramen magnum



Medulla oblongata

Meninges

Vertebral arteries

Spinal roots of accessory nerves



2.2  FORAMINA IN THE BASE OF THE ADULT

SKULL

The foramina in the base of the skull allow major nerves and

blood vessels to course through the skull through each opening. Pressure, traction, and masses can damage structures traversing these small spaces that snugly confine the structures.



29



CLINICAL POINT

The foramina of the skull are narrow openings that allow the passage of nerves and blood vessels. Under normal circumstances, there

is enough room for comfortable passage of these structures �without

traction or pressure. However, with the presence of a tumor at a

�foramen, the passing structures can be compressed or damaged.

A tumor at the internal acoustic meatus can result in ipsilateral facial and vestibuloacoustic nerve damage, and a tumor at the jugular

�foramen can result in damage to the glossopharyngeal, vagus, and spinal accessory nerves.



30



Overview of the Nervous System



Temporal bone

Sphenoid bone

Temporal fossa

Zygomatic arch

Condylar process of mandible

Mandibular notch

Coronoid process of mandible

Lateral pterygoid plate (broken line)

Hamulus of medial pterygoid plate (broken line)

Pterygomandibular raphe (broken line)



Mastoid process

External acoustic meatus

Mandible



Ramus

Angle

Body



Atlas (C1)

Styloid process

Axis (C2)

Stylomandibular ligament



Stylohyoid ligament

Hyoid bone

Spine of sphenoid bone

Foramen spinosum

Foramen ovale



C3 vertebra



Body

Lesser horn

Greater horn



C7 vertebra



Epiglottis

Thyroid cartilage

Cricoid cartilage

Trachea



T1 vertebra



1st rib



Sphenopalatine foramen

Pterygopalatine fossa

Choanae (posterior nares)



Tuberosity of maxilla

Infratemporal fossa

Alveolar process of maxilla



Lateral plate

Medial plate of pterygoid process

Hamulus

Pyramidal process of palatine bone



2.3  BONY FRAMEWORK OF THE HEAD

AND NECK

The skull provides bony protection for the brain. The spine,

consisting of vertebrae and their intervertebral disks, �provides



bony protection for the spinal cord. The spine and skull

�articulate at the foramen magnum, where the C1 vertebral

body (the atlas) abuts the occipital bone.



Skull and Meninges



Arachnoid granulation



31



Venous lacuna

Skin

Galea aponeurotica

Epicranium

Calvaria

Dura mater (outer and inner layers)

Subdural space (potential)

Arachnoid

Subarachnoid space

Pia mater

Cerebral hemisphere

Superior sagittal sinus



Epidural space (potential)



Arachnoid granulation

Arachnoid granulation indenting skull (foveola)

Venous lacuna



Arachnoid



Dura mater

(outer layer)

Dura mater

(inner layer)



Subarachnoid space



Inner layer of dura mater

Falx cerebri



Inferior sagittal sinus



2.4  SCHEMATIC OF THE MENINGES AND THEIR

RELATIONSHIPS TO THE BRAIN AND SKULL

The meninges provide protection and support for neural tissue in the central nervous system. The innermost membrane,

the pia mater, adheres to every contour of neural tissue, including sulci, folia, and other infoldings. It adheres tightly to

glial endfoot processes of astrocytes; this association is called

the pial-glial membrane. The arachnoid mater, a fine, lacy

membrane external to the pia, extends across the neural sulci

and foldings. The space between these two membranes is the

subarachnoid space, a space into which the cerebrospinal fluid

flows, providing buoyancy and protection for the brain. Arteries and veins run through the subarachnoid space to and

from the central nervous system. The rupture of an arterial

aneurysm in a cerebral artery results in a subarachnoid hemorrhage. The dura mater, usually adherent to the inner arachnoid, is a tough protective outer membrane. It splits into two

layers in some locations to provide channels for the venous

blood, the venous sinuses. The arachnoid granulations, oneway valves, extend from the subarachnoid space into the venous sinuses, especially the superior sagittal sinus, allowing

cerebrospinal fluid to drain into the venous blood and return



Pia mater



Middle meningeal

artery and vein



to the heart. Blockage of these arachnoid granulations (e.g., in

acute purulent meningitis) can result in increased intracranial

pressure. Cerebral arteries and veins traverse the subarachnoid

space. The veins, called bridging veins, drain into the dural sinuses. As they enter the sinus, these bridging veins are subject

to tearing in cases of head trauma. If there is atrophy in the

brain, as occurs with age, these veins may tear with relatively

minor head trauma; in younger adults, more severe head trauma is needed to tear these bridging veins. Such tearing permits venous blood to accumulate in the subdural space as it

dissects the inner dura from the arachnoid. This process may

be gradual (chronic subdural hematoma) in older individuals or may be abrupt (acute subdural hematoma) with severe

head trauma. A subdural hematoma, especially when it occurs

acutely, may be life-threatening as the result of increased intracranial pressure caused by accompanying edema and by the

accumulation of the blood in the hematoma itself. The dura is

closely adherent to the inner table of the skull. A skull fracture

may tear a branch of the middle meningeal artery, permitting

arterial blood to dissect the dura from the skull, resulting in an

epidural hematoma.



32



Overview of the Nervous System



Temporal Fossa Hematoma

Shift of normal midline structures



Skull fracture crossing

middle meningeal artery



Compression of posterior

cerebral artery



Shift of brain stem to opposite

side may reverse lateralization

of signs by tentorial pressure

on contralateral pathways



Herniation of

temporal lobe

under tentorium

cerebelli



Herniation of cerebellar tonsil

Compression of oculomotor (III) nerve leading to

ipsilateral pupil dilatation and third cranial nerve palsy



Compression of corticospinal and associated

pathways, resulting in contralateral hemiparesis,

deep tendon hyperreflexia, and Babinski’s sign



Acute Subdural Hematoma

Subfrontal

Hematoma

Frontal trauma:

headache, poor

cerebration,

intermittent

disorientation,

anisocoria



Posterior Fossa Hematoma

Occipital trauma and/or

fracture: headache,

meningismus, cerebellar

and cranial nerve signs,

Cushing’s triad

Section showing acute subdural hematoma on right side

and subdural hematoma associated with temporal lobe

intracerebral hematoma (“burst” temporal lobe) on left



2.5  HEMATOMAS

Epidural hematomas occur with trauma or skull fractures

that tear meningeal arteries (especially middle meningeal artery branches). Blood from the tear dissects the outer layer of

the dura from the skull, forming a space-occupying mass in

what was normally only a potential space. The hematoma may

compress adjacent brain tissue, producing localized signs, and

may also cause herniation of distant brain regions across the

free edge of the tentorium cerebelli (a transtentorial herniation) or across the falx cerebri (a subfalcial herniation). Such

herniation may produce changes in consciousness, breathing,

and blood pressure and altered motor, pupillary, and other



neurological signs. It may be fatal. Severe head trauma in an

adult may tear bridging veins that lead from the brain through

the subarachnoid space and into the dural sinuses, especially

the superior sagittal sinus. The subsequent venous bleeding

dissects the arachnoid membrane from the inner layer of the

dura, and the blood accumulates as a subdural hematoma. The

subdural space is normally only a potential space. Some of the

proteins and other solutes in the hematoma attract edema,

adding fluid accumulation to the hematoma and further exacerbating the space-occupying nature of the bleed. A subdural

hematoma also may be associated with a bleeding directly into

the brain, an intracerebral hematoma.



3



BRAIN



3.1



S

 urface Anatomy of the Forebrain: Lateral View



3.2



L

 ateral View of the Forebrain: Functional Regions



3.3



L

 ateral View of the Forebrain: Brodmann’s Areas



3.4



A

 natomy of the Medial (Midsagittal) Surface of the Brain in Situ



3.5



A

 natomy of the Medial (Midsagittal) Surface of the Brain, with

Brain Stem Removed



3.6



M

 edial Surface of the Brain



3.7



A

 natomy of the Basal Surface of the Brain, with the Brain Stem

and �Cerebellum Removed



3.8



B

 asal Surface of the Brain: Functional Areas and Brodmann’s Areas



3.9



B

 rain Imaging: Computed Tomography Scans, �Coronal and Sagittal



3.10



B

 rain Imaging: Magnetic Resonance Imaging, Axial and Sagittal

T1-Weighted Images



3.11



B

 rain Imaging: Magnetic Resonance �Imaging, Axial and Sagittal

T2-Weighted Images



3.12



P

 ositron Emission Tomography Scanning



3.13



H

 orizontal Brain Sections Showing the Basal �Ganglia



3.14



M

 ajor Limbic Forebrain Structures



3.15



C

 orpus Callosum



3.16



C

 olor Imaging of the Corpus Callosum by Diffusion Tensor Imaging



3.17



H

 ippocampal Formation and Fornix



3.18



T

 halamic Anatomy



3.19



T

 halamic Nuclei



33



34



Overview of the Nervous System



Central sulcus

Precentral gyrus

Precentral sulcus

Frontal (F), frontoparietal (FP)

and temporal (T) opercula



Superior (superomedial) margin of cerebrum

Postcentral gyrus

Postcentral sulcus

Supramarginal gyrus

Superior parietal lobule

Intraparietal sulcus



Superior frontal gyrus



Inferior parietal lobule



Superior frontal sulcus



Angular gyrus

Middle frontal gyrus



Parietooccipital sulcus

Transverse

occipital sulcus



Inferior frontal sulcus

Inferior frontal gyrus



FP

F



Calcarine fissure



T



Occipital pole



Frontal pole

Anterior ramus

Ascending ramus

Posterior ramus

Temporal pole Superior temporal gyrus

Superior temporal sulcus

Middle temporal gyrus

Inferior temporal sulcus

Parietal lobe



Lunate sulcus

(inconstant)

Inferior (inferolateral)

margin of cerebrum



Lateral (sylvian) fissure



Preoccipital notch



Inferior temporal gyrus



Frontal lobe

Occipital lobe



Central sulcus of insula

Temporal lobe



Circular sulcus of insula

Insula



3.1  SURFACE ANATOMY OF THE FOREBRAIN:

LATERAL VIEW

The convolutions of the cerebral cortex allow a large expanse

of cortex to be compactly folded into a small volume, an adaptation particularly prominent in primates. Major dependable landmarks separate the forebrain into lobes; the lateral

(sylvian) fissure separates the temporal lobe below from the

parietal and frontal lobes above, and the central sulcus separates the parietal and frontal lobes from each other. Several of

the named gyri are associated with specific functional activities, such as the precentral gyrus (motor cortex) and the postcentral gyrus (primary sensory cortex). Some gyri, such as the

superior, middle, and inferior frontal and temporal gyri, serve

as anatomical landmarks of the cerebral cortex. The insula,

the fifth lobe of the cerebral cortex, is deep to the outer cortex

and can be seen by opening the lateral fissure.



Short gyri

Limen

Long gyrus



CLINICAL POINT

Some functional characteristics of the cerebral cortex, such as longterm memory and some cognitive capabilities, cannot be localized

easily to a particular gyrus or region of cortex. However, other functional capabilities are regionally localized. For example, the inferior

frontal gyrus on the left contains the neuronal machinery for expressive language capabilities; the occipital pole, particularly along the upper and lower banks of the calcarine fissure, are specialized for visual

processing from the retino-geniculo-calcarine system. Some very discrete lesions in further processing sites such as vision-related regions

of the temporal lobe can result in specific deficits, such as agnosia for

the recognition of faces or the inability to distinguish animate objects.

This knowledge provides some clues about how feature extraction in

sensory systems might be achieved in neuronal networks.



Brain



Central sulcus



Supplemental

motor cortex



Superior

parietal lobule



Primary

motor

cortex

Frontal

eye fields



Premotor

cortex



Primary

somatosensory

cortex

Primary

trigeminal

region of



Broca's

area

motor

cortex



35



Wernicke's



Secondary area

somatosensory

cortex

somatosensory

cortex

Primary

Auditory cortex



Multisensory

association

areas of cortex



Visual

association

areas of cortex



Primary

visual

cortex



Lateral fissure



3.2  LATERAL VIEW OF THE FOREBRAIN:

�FUNCTIONAL REGIONS

Some circumscribed regions of the cerebral hemisphere are

associated with specific functional activities, including the

motor cortex, the supplemental and premotor cortices, the

frontal eye fields, the primary sensory cortex, and other association regions of the sensory cortex. Part of the auditory

cortex is visible at the inferior edge of the lateral fissure (the

transverse temporal gyrus of Heschl). Part of the visual cortex is visible at the occipital pole. Language areas of the left

hemisphere include Broca’s area (expressive language) and

Â�Wernicke’s area (receptive language). Damage to these cortical regions results in loss of specific functional capabilities.

There is some overlap between functional areas and named

gyri (e.g., the motor cortex and the precentral gyrus), but

there is no absolute concordance.



CLINICAL POINT

Some specific regions (gyri) of the cerebral cortex, such as the precentral gyrus (primary motor cortex) and the postcentral gyrus (primary

somatosensory cortex), demonstrate topographic organization. Thus,

information from the contralateral hand and arm are localized laterally, the body is represented more medially, and the lower extremity is

represented along the midline and over the edge into the paracentral

lobule. The face and head are represented in far lateral regions, just

above the lateral fissure. This has important functional implications;

damage to selected regions such as the midline territory, which is supplied with blood from the anterior cerebral artery, results in somatosensory loss and paresis in the contralateral lower extremity, while

sparing the upper extremity.