Apmle: Part 1 Comprehensive Review

APMLE

PART 1

Comprehensive Review

A convenient, effective and high-yield review course for Part 1.

An essential study guide for the American Podiatric Medical Licensing Examination (APMLE) Part1

Podiatry Boards Prep

Copyright © 2015 by Podiatry Boards Prep.

Library of Congress Control Number:  2015912217

ISBN:  Hardcover   978-1-5035-9091-5

            Softcover      978-1-5035-9090-8

            eBook           978-1-5035-9089-2

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Rev. date: 10/07/2015

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Contents

Anatomy

Neuroscience

Osteology/Ossification

Bones: General Features

Bones: Particular Features

Medial Side of the Thigh

Gluteal Region

Back of the Thigh

Popliteal Fossa

Leg

Anterior Compartment of the Leg

Dorsum of the Foot

Lateral Compartment of the Leg

Posterior Compartment of the Leg

Sole of the Foot

Segmental Cutaneous Innervation of the Lower Limb

Lymphatics of the Lower Limb

Joints of the Lower Limb

Histology

Biochemistry

Cell Biology

Cell and Muscle Physiology

Endocrinology

GI Physiology

Renal Physiology

Respiratory Physiology

Immunology

General Pathology

Pathology

Dermatology

Endocrinology

Gestroenterology

Hematology

Nephrology

Neurology

Pulmonology

Miscellaneous

Pharmacology

ANATOMY

HEAD AND NECK

*  Pharyngeal arches: mesoderm + neural crest

ƒ  1st arch: formed muscles of mastication, tensor tympani, tensor palatine, incus, malleus, maxilla, mandible, and mandibular nerve (CN-5-III)

ƒ  2nd arch: formed muscles of facial expression, stapedius, stapes,

ƒ  styloid process, lesser horn and upper body of hyoid and facial nerve (CN-7)

ƒ  3rd arch: formed stylopharengeus muscle, greater horn and lower

ƒ  body of hyoid and glossopharyngeal nerve (CN-9)

ƒ  4th arch: formed cricothyroid muscles, right subclavian artery, laryngeal cartilage, and superior laryngeal nerve (a branch of vagus nerve [CN-10])

ƒ  5th arch: obliterated normally

ƒ  6th arch: all laryngeal muscles except cricothyroid muscle, laryngeal cartilage, and recurrent laryngeal nerve (a branch of vagus nerve [CN-10])

ƒ  It is very easy to remember the nerve supply of different derivatives of all arches. The cranial nerve derived from a particular arch is responsible for supplying them!

*  Pharyngeal pouches: endoderm

1.  Epithelial lining of auditory tube and middle ear cavity

2.  Epithelial lining of crypts of palatine tonsil

3.  Thymus, inferior parathyroid gland (absent in DiGeorge)

4.  Ultimobranchial body, superior parathyroid gland

ƒ  Neural crest cells migrate into the ultimobranchial body to form parafollicular cells of thyroid gland (secrete calcitonin).

*  Pharyngeal grooves: ectoderm

ƒ  Epithelial lining of external auditory meatus All other grooves are obliterated

*  Paranasal Sinuses

ƒ  Sphenoidal – in superior meatus

ƒ  Maxillary, frontal, anterior, and middle ethmoidal – in middle meatus

ƒ  Posterior ethmoidal – in superior meatus

ƒ  Hiatus semilunaris (in middle meatus) – frontal, maxillary, and anterior ethmoidal sinus

ƒ  Bulla ethmoidalis (in middle meatus) – middle ethmoidal sinus

*  Ansa Cervicalis (C1, 2, 3)

ƒ  Supply three strap muscles – sternohyoid, omohyoid (both bellies), sternothyroid

ƒ  Remaining two strap muscles – thyrohyoid, giniohyoid (supplied by C1 fiber)

ƒ  Posterior belly of digastric and stylohyoid – supplied by CN-7 (facial N)

ƒ  Anterior belly of digastric and mylohyoid – supplied by CN-5-III (mandibular N)

ƒ  Tongue: anterior 2/3 – general sensation – CN-5-III (mandibular N) taste sensation – CN-7 (facial N)

posterior 1/3 – general and taste sensation – CN-9

ƒ  All themuscles of tongue innervated by CN-12 except palatoglossus.

ƒ  Palatoglossus is innervated by CN-10.

ƒ  Test for CN-12 lesion: on protrusion of tongue, tongue deviates toward the site of lesion

ƒ  Protrusion of tongue – genioglossus muscle

ƒ  All muscles of mastication are innervated by mandibular N.

ƒ  All muscles of pharynx supplied by CN-10 except tensor palatine

ƒ  Tensor palatine (mandibular N) elevates the soft palate to avoid regurgitation of food/liquid in nasopharynx during swallowing.

*  Muscles of Larynx

ƒ  Lateral cricoarytenoid – adduct vocal cord

ƒ  Posterior cricoarytenoid – abduct vocal cord

ƒ  Thyroarytenoid – sphincter of vestibule, narrowing the laryngeal inlet

ƒ  Cricothyroid – lengthen and stretch the vocal cord

ƒ  Paired laryngeal cartilage – arytenoid, corniculate, and cuneiforms

ƒ  Single laryngeal cartilage – cricoid, thyroid, and epiglottis

ƒ  All muscles of larynx are supplied by recurrent laryngeal nerve

ƒ  except cricothyroid (superior laryngeal nerve).

*  Important Points about Cranial Nerve Lesions

ƒ  CN-1 (olfactory N): loss of smell

ƒ  CN-2 (optic N): different signs and symptoms according to the site of the lesion (see neuroscience notes)

ƒ  CN-3 (occulomotor N): loss of accommodation, ptosis, outward deviation (LR)

ƒ  CN-4 (trochlear N): weakness of downward and inward eye movement (SO)

ƒ  CN-6 (abducent N): inability to look laterally (weak LR, inward deviation)

ƒ  CN-5 (trigeminal N): the jaw deviates to the weak side when the mouth is opened, loss of corneal reflex, loss of sensation on face

ƒ  CN-7 (facial N): ipsilateral paralysis of all facial muscles (Bell’s palsy)

ƒ  CN-8 (vestibulocochlear N): unilateral sensorineural deafness, vestibular symptoms (balance and postural problem)

ƒ  CN-9 (glossopharyngeal N): loss of sensation on posterior 1/3 of tongue, loss of gag reflex (gag reflex – sensory [CN-9]; motor [CN-10])

ƒ  CN-10 (vagus N): uvula deviates opposite side of lesion

ƒ  CN-11 (accessory N): loss of shoulder shrugging (trapezius) and weakness of sternocleidomastoid

ƒ  CN-12 (hypoglossal N): tongue deviates toward the site of lesion on protrusion

ƒ  All cranial nerve lesion produce defect on the same side except

ƒ  CN-10 (vagus N)

ƒ  Pupillary Reflex: sensory (CN-2); motor (CN-3)

ƒ  Corneal Reflex: sensory (CN-5, ophthalmic division); motor (CN-3)

THORAX

ƒ  Breast: lateral ½ - axillary lymphnode medial ½ - parasternal lymphnode

ƒ  1–7: true ribs

ƒ  8–10: false ribs – attached to the costal cartilage of the rib

ƒ  11–12: false ribs – no anterior attachment (floating ribs)

ƒ  Intercostal Muscles Blood Supply

ƒ  Collateral between internal thoracic artery and aorta produce rib notching in coarctation of the aorta

ƒ  Bottom of the pleura is two ribs lower than the bottom of the lung

ƒ  Any penetrating injury below fourth intercostal space on the right side can injure the liver

ƒ  Roots of phrenic nerve – C3, 4, 5

ƒ  Bronchopulmonary segments – ten on the right, eight on the left

„  Borders of Heart

ƒ  Right – right atrium (3rd to 6th ribs)

ƒ  Left – left ventricle (2nd to 5th rib)

ƒ  Superior – right and left auricles + conus arteriosus of right ventricle

ƒ  Apex – tip of the left ventricle

ƒ  Ant wall – right ventricle

ƒ  Post wall – left atrium

ƒ  Diaphragmatic wall – left ventricle

ƒ  Pericardial space – space between epicardium and parietal pericardium

„  Right and Left Atrium

ƒ  Auricle: pectinate muscles (rough part)

ƒ  Crista terminalis: ventricle ridge that separates smooth and rough parts

ƒ  Sinus venerum: smooth walled (formed by SVC and IVC)

„  Right and Left Ventricle

ƒ  Trabaculae carneae (same as pectinate muscle)

ƒ  Papillary muscles

ƒ  Chordea tendinae

ƒ  Infundibulum (right ventricle)

ƒ  Aortic vestibule (left ventricle)

„  Right Coronary Artery

ƒ  SA node, AV node

ƒ  Right atrium, right ventricle

ƒ  Part of left atrium and ventricle

ƒ  Posterior part of the interventricular septum (In left dominant, it is supplied by left circumflex artery)

„  Left Coronary Artery

ƒ  Left anterior descending: most part of interventricular septum, apex of the left ventricle

ƒ  Circumflex: left atrium, left ventricle, lateral wall

„  Venous Drainage of the Heart

ƒ  Great cardiac vein: travel with anterior interventricular artery

ƒ  Middle cardiac vein: travel with posterior interventricular artery (both open in coronary sinus)

ƒ  Venae cordis minimae (Thebesian vein) and anterior cardiac vein

ƒ  directly open in the chambers of heart

ƒ  Coronary sinus travel in posterior coronary sulcus and open in right atrium

ƒ  Thoracic Duct: starts in the abdomen from cisterna chyli (L2, 3 level)

ƒ  Drain: left upper limb (UL)

left thorax, left head and neck (H&N), pelvis, abdomen and lower limb (LL)

ƒ  Empty in left brachiocephalic vein

ƒ  Found in posterior and superior mediastinum

„  Right Lymphatic Duct

ƒ  Drain: right thorax and right H&N, right UL

ƒ  Empty in right brachiocephalic vein

„  Azygos System of Veins

ƒ  Right side – azygos

ƒ  Left side – hemiazygos and accessory hemiazygos (both drain to azygos vein)

ƒ  The posterior thoracic and abdominal walls are drained by the azygos system of veins

ƒ  Azygos – arise from the posterior aspect of IVC (inferior vena cava)

ƒ  Hemiazygos – arise from the left renal vein

ƒ  Azygos veins empty into superior vena cava

ƒ  Openings in the Diaphragm: caval (T8 plus right phrenic nerves) esophageal (T10 plus vegus nerve) aortic (T12 plus azygos vein and thoracic duct)

UPPER LIMB

ƒ  Musculocutaneous N (C5 to C7): all the muscles of the anterior compartment of arm (biceps, brachialis, coracobrachi)

ƒ  Long thoracic N (C5 to C7): serratus anterior

ƒ  Axillary N (C5, C6): deltoid and teres major muscle (deltoid – origin: clavicle and acromion)

*  Median N (C5 to T1): supracondylar region of humerus

ƒ  All muscles of anterior compartment of forearm except one and a half muscles (flexor carpi ulnaris and ulnar half of the flexor digitorum profundas)

ƒ  Three thenar muscles and 1st and 2nd lumbricals

ƒ  If injured: ulnar deviation of hand on flexion

*  Ulnar N (C7 to T1): medial epicondyle of humerus

ƒ  Flexor carpi ulnaris

ƒ  Ulnar half of flexor digitorum profundas

ƒ  3rd and 4th lumbricals

ƒ  All introssei muscles

*  Radial N (C5 to T1): shaft of the humerus

ƒ  The posterior muscles of arm and forearm (there are no muscles in the posterior of the hand)

ƒ  Upper trunk (C5, C6): axillary N, musculocutaneous N

Erb’s palsy – muscles of shoulder and anterior arm (waiter’s tip)

Arm – medially rotated and adducted

Forearm – extended and pronated

ƒ  Lower trunk (C8, T1)

Klumpke’s palsy – loss of the muscles of forearm and hand

ƒ  Lumbricals (4): flex metacarpophalangeal joint and extend interphalangeal joint

ƒ  Introssei (7): four dorsal (abduct fingers) and three palmar (adduct fingers)

*  Abductors of Thumb

ƒ  Abd pollicis bravis – median N

ƒ  Abd pollicis longus – radial N (posterior interosseous nerve), so patient can abduct his hand in median N injury

*  Flexors of Thumb

ƒ  Flex pollicis bravis – median N

ƒ  Flex pollicis longus – median N (anterior interosseous nerve)

*  Adductors of Thumb

ƒ  Adductor pollicis – ulnar N

ƒ  Therefore, muscles of thumb get nerve supply from all three nerves (radial, median, and ulnar)

*  Test for Injury of Different Nerves

ƒ  Axillary N: loss of abduction of the arm to the horizontal level

ƒ  Radial N: loss of extensors, wrist drop

ƒ  Median N: loss of opponens; patient can’t oppose thumb (can’t count with fingers)

ƒ  Ulnar N: loss of abd and add of fingers (interossei); ask patient to

ƒ  hold paper in between two fingers

ƒ  Long thoracic N: winging of the scapula

ABDOMEN

ƒ  Layers of the Abdominal Wall (From Outside to Inside)

1.  Skin

2.  Superficial fascia

3.  Deep fascia

4.  External (ext) oblique

5.  Internal (int) oblique

6.  Transversus abdominis

7.  Transversalis fascia

8.  Parietal peritoneum

*  Superficial fascia: There are two types of superficial fascia. One is Camper’s fascia, which is mainly composed of fat, and another is Scarpa’s fascia, which is membranous. Scarpa’s fascia is continuous with fascialata of the thigh, Dartos fascia of the scrotum, and Colle’s fascia of the perineum.

ƒ  Muscles of abdominal wall: All three muscles of the abdomen consist of its covering fascia, muscles, and its aponeurosis.

ƒ  The free border of the external oblique aponeurosis forms the

ƒ  inguinal ligament.

ƒ  Superficial inguinal ring is an opening in the ext oblique aponeurosis.

ƒ  Int oblique and transversus aponeurosis muscles fibers join to form

ƒ  conjoint tendon.

ƒ  Deep inguinal ring begin as an outpouching of the transversalis fascia.

ƒ  Arcualte line: between umbilicus and pubis

ƒ  Above arcuate line: rectus sheath is covered by all three muscles’ aponeuroses, both anteriorly and posteriorly

ƒ  Below arcuate line: covered only anteriorly by three muscles’ aponeuroses; posteriorly, it is covered by transversalis fascia only

*  Boundaries of Inguinal Canal

ƒ  Roof: int oblique and transversus abdominis

ƒ  Ant wall: aponeuroses of ext oblique and int oblique

ƒ  Floor: inguinal ligament

ƒ  Post wall: transversalis fascia (weaker part) and conjoint tendon (reinforce medial part)

*  Boundaries of Femoral Canal

ƒ  Anterior – inguinal ligament

ƒ  Posterior – pubis

ƒ  Medial – lacunar ligament

ƒ  Lateral – femoral vein

ƒ  Direct inguinal hernia – abdominal contents herniate through a weak point in the fascia of the abdominal wall and into the inguinal canal

ƒ  Indirect inguinal hernia – abdominal contents protrude through the deep inguinal ring (failure of closure of processus vaginalis)

ƒ  Femoral hernia – inferior and lateral to the pubic tubercle

ƒ  Processus vaginalis – developmental outpouching of the peritoneum: it precedes the testis in their descent down within

ƒ  the gubernaculum, and closes—the remaining portion around the testis becomes tunica vaginalis

ƒ  Psoas major – chief flexor of hip

ƒ  Foregut: up to first part of duodenum

ƒ  Midgut: up to proximal two-thirds of the transverse colon

ƒ  Spleen is not a derivative of foregut, but it is supplied by foregut artery (branch of celiac artery)

ƒ  Greater omentum: gastrophrenic, gastrocolic, and gastrosplenic ligaments

ƒ  Lesser omentum: hepatoduodenal and hepatogastric ligaments

ƒ  Greater and lesser peritoneal sacs are separated by the hepatogastric ligament on the right (surgical access to lesser sac) and by the gastrosplenic ligament on the left

ƒ  Epiploic foramen: an opening into omental bursa (lesser sac); a finger in the epiploic foramen touches the hepatoduodenal ligament anteriorly and IVC posteriorly

ƒ  Free edge of lesser omentum (hepatoduodenal ligament) contain

ƒ  three structures: hepatic portal vein, common bile duct, and hepatic artery

ƒ  The spleenorenal ligament contains the splenic artery and vein.

ƒ  The gastrosplenic ligament contains short gastric vessels and left gastroepiploic vessels.

ƒ  The hepatogastric ligament contains the right and left gastric

ƒ  arteries near the stomach.

ƒ  Retroperitoneal organs: duodenum, ascending colon, descending colon, kidneys, and adrenal glands

ƒ  Branches of celiac trunk: left gastric artery (lesser curvature),

ƒ  common hepatic artery, and splenic artery

ƒ  Hepatic artery: proper hepatic artery, cystic artery, gastroduodenal artery, right gastric artery (lesser curvature)

ƒ  Splenic artery: left gastroepiploic artery, dorsal pancreatic artery,

ƒ  short gastric artery

*  Blood Supply of Stomach

ƒ  Left gastric: proximal lesser curvature

ƒ  Right gastric: distal lesser curvature

ƒ  Left gastroepiploic: proximal greater curvature

ƒ  Right gastroepiploic: distal lesser curvature

ƒ  Short gastric: short greater curvature above splenic artery

*  Portosystemic Anastomoses (Branch of Portal Vein + Branch of Systemic Vein)

1.  Lower esophagus: esophageal branch of left gastric (portal) and azygos vein (systemic)

2.  Upper anal canal: superior rectal vein (portal) and middle / inferior rectal veins (systemic)

3.  Umbilicus: vein of ligamentum teres (portal) and superior / inferior epigastric vein (systemic)

4.  Bare area of liver: hepatic/portal vein (portal) and inferior phrenic vein (systemic)

5.  Patent ductus venosus (rare): left branch of portal vein (portal) and IVC (systemic)

6.  Retroperitoneal: colonic veins (portal) and body wall veins (systemic)

*  Kidney

ƒ  Pronephros – cervical intermediate mesoderm (fourth week of gestation)

ƒ  Mesonephros – thoracic and lumbar intermediate mesoderm (fifth week)

ƒ  Metanephros – lumbar and sacral intermediate mesoderm (fifthweek)

ƒ  Tubule regress and duct persists

ƒ  Pronephros – nonfunctional

ƒ  Mesonephric duct forms (Wolffian duct) – epididymidis, ductus (vas) deferens, ejaculatory duct, seminal vesicle

ƒ  Metanephros – ureteric bud (also known as metanephric duct, diverticulum of metanephric duct) and metanephrogenic blastema

ƒ  Ureteric bud forms – ureters, renal pelvis, collecting ducts, major and minor calyces

ƒ  Metanephrogenic blastema (lumbar and sacral mesoderm) forms – renal tubules (PCT, DCT, loop of Henle, Bowman’s capsule) and definitive glomerulus

ƒ  Upper and largest part of urogenital sinus becomes urinary bladder

ƒ  Male urethra: prostatic, membranous, and proximal penile derived from urogenital sinus; distal penile derived from glans of penis

ƒ  Female urethra: upper two thirds derived from mesonephric duct; lower one third derived from urogenital sinus

ƒ  Prostate gland in male is also derived from urogenital sinus

*  Relationship of Ureters

ƒ  Lies on anterior surface of psoas major

ƒ  Crossing ext iliac as they pass over the pelvic brim

ƒ  Posterior to the uterine artery in female

*  Blood Supply of Kidney

ƒ  Interlobar arteries

ƒ  Arcuate artery

ƒ  Interlobular artery (branch of arcuate artery)

ƒ  Afferent arterioles leads to capillary tuft of glomeruli

*  Blood supply of urinary bladder: internal iliac artery

*  Content of Superior Perineal Pouch

ƒ  Bartholin’s gland (in female)

ƒ  Cura of penis or clitoris

ƒ  Bulb of penis or bulb of vestibule

ƒ  Ischiocavernous muscle

ƒ  Bulbospongious muscle

*  Content of Deep Perineal Pouch

ƒ  Bulbourethral gland (in male)

ƒ  Sphincter urethrae muscle

ƒ  Deep transverse perineal muscle

ƒ  Descent of the testis: The testis develops in the extraperitoneal layer (between layer 7 and 8) and descends from abdomen into scrotum. When it starts descending from the abdomen into the scrotum, its covers of fascia comes in its way. Three fascias (internal spermatic fascia, cremasteric fascia, and external spermatic fascia) cover it from inside to outside respectively. These three fascias derived from transversalis, internal oblique, and external oblique fascias respectively. Skin and Scarpa’s fascia make scrotum. When the testis starts decent, it brings part of the peritoneum with it (processus vaginalis) which is obliterated after birth.

*  Testis: seminiferous tubule + stroma (contain interstitial cells [Leyding cells])

ƒ  Seminiferous tubule: site of spermatogenesis

ƒ  Sertoli cells: irregular columnar cells extend from the basal lamina to the lumen

-  Provide blood-testes barrier

-  Tight junction between Sertoli cells divide seminiferous tubule in two compartment: basal compartment (spermatogonia) and adluminal compartment (spermatocytes and spermatids)

ƒ  Spermatogonia are near basal lamina and between two sertoli cells (all germ cells are between two sertoli cells)

ƒ  Sperm undergoes maturation in epididymis

ƒ  Seminal vesicles secrete fluids that contain fructose and serve as an energy source for the sperm.

*  Ovary: cortex: ovarian follicles medulla: nerves and blood vessels

ƒ  Ovarian follicles: composed of oocytes surrounded by follicular (granulosa) cells

-  Primordial follicle: primary oocytes surrounded by single layer of flattened follicular cells

-  Primary follicle: primary oocytes + one or more layers of cuboidal like follicular cells

-  Secondary follicle: follicular cavity (antrum), cumulus oophorus, corona radiata, thica interna (secrete androgens that convert into estradiol by granulosa cells), thica externa, zona pellucida around the oocyte (zona pellucida is PAS positive)

-  Graafian follicle: mature follicle extends through cortex

-  Ovulation: increase in antral fluid causes rupture of follicle and ovum along with corona radiata passes out of the ovary

-  Follicular cavity changes occur leads to formation of corpus lutem

-  Thica interna – thica lutin interna (in corpus lutem) – secrete estrogen

-  Thica externa – granulosa lutin cells (in corpus lutem) – secrete progesterone

-  Corpus lutem persists until three months by hCG secreted by embryo. After the 40th day, the placenta produces progesterone necessary to maintain pregnancy

„  Spermatogenesis: primordial germ cells arrive in the indifferent gonad at week 4 and remain dormant until puberty

ƒ  At puberty, primordial germ cells differentiate into type-A spermatogonia, which serve as stem cells throughout adult life

ƒ  Oogenesis: primordial germ cells arrive in the indifferent gonad at week 4 and differentiate into oogonia

ƒ  Oogonia enter miosis-I to form primary oocytes. All primary oocytes formed by 5th month of fetal life, remain arrested in prophase (diplotene) of miosis-I until puberty

ƒ  At puberty, complete miosis-I and become secondary oocyte and polar body

ƒ  Secondary oocyte arrested in metaphase of miosis-II and is ovulated

ƒ  At fertilization, secondary oocyte complete miosis-II to form mature oocyte and polar body

ƒ  Miosis-I: synapsis (pairing), crossing over, disjunction (without centromere splitting)

ƒ  Miosis-II: no synapsis, no crossing over, disjunction with centromere splitting

NEUROSCIENCE

ƒ  Forebrain – telencephalon (cerebral cortex, basal ganglia, lateral ventricles, and olfactory bulb) and diencephalon (prethalamus, thalamus, hypothalamus, subthalamus, epithalamus, pretectum, and the posterior pituitary gland)

ƒ  Midbrain – mesencephalon (midbrain, cerebral aqueduct)

ƒ  Hindbrain – metencephalon (pons and cerebellum) and myelencephalon (medulla); the 4th ventricle forms from both metencephalon and myelencephalon

ƒ  Anteriorpituitarygland– isanoutgrowthoforalectoderm(Rathke’s pouch). Remnant of Rathke’s pouch forms craniopharyngioma that compress optic chiasm and produce bitemporal heteronymous hemianopsia

ƒ  Neural crest form – adrenal medulla, primary sensory neurons and postganglionic autonomic neurons (cell bodies in ganglia [peripheral nervous system {PNS}])

ƒ  Neural tube form – skeletal motor neurons and preganglionic autonomic neurons (cell bodies in SC [central nervous system {CNS}])

ƒ  Schwann cells make myelin for PNS

ƒ  Oligodendrocytes make myelin for CNS

ƒ  Optic N (CN-2) is an outgrowth of brain so its myelin is formed by oligodendrocytes. CN-2 is affected in multiple sclerosis

ƒ  Sympathetic outflow – T1 to L2 (descending hypothalamic fibers drive all Pre- ganglionic sympathetic nerve fibers)

ƒ  Parasympathetic outflow – CN-3, 7, 9, 10 and S-2, 3, 4

ƒ  Optic canal – CN-2 (optic N) and ophthalmic artery

ƒ  Rotundum – maxillary N (CN-5 second division), V2

ƒ  Ovale – mandibular N (V3), ophthalmic division V1 pass through superior orbital fissure

ƒ  Spinosum – middle meningeal artery (epidural hematoma)

ƒ  Lacerum – nothing

ƒ  Internal auditory meatus – CN-7, 8

ƒ  Jugular foramen – CN-9, 10, 11, sigmoid sinus

ƒ  Hypoglossal canal – CN-12

ƒ  Foramen magnum – CN-11, vertebral artery, spinal cord – brain stem junction

ƒ  Spinal cord (SC)

ƒ  Cell bodies of sensory fibers – dorsal root ganglion (so not in SC)

ƒ  Cell bodies of motor fibers – ventral horn of gray matter of SC

ƒ  Dorsal root of spinal cord – sensory fibers

ƒ  Ventral root of spinal cord – motor fibers

ƒ  UMN has net inhibitory effect on reflex; therefore in UMN lesion, there is hyperreflexia, spastic paralysis, and Babinski sign present (extension of toes)

ƒ  Dorsal column – medial lemniscal system (DC): three neurons

ƒ  Discriminative touch, joint position sense, vibratory and pressure sensation from the trunk and limbs

ƒ  Fasciculus gracillis (LL): found at all level of SC (LL = lower limb)

ƒ  Fasciculus cuneatus (UL): found only at upper thoracic and cervical level of SC

ƒ  Cell bodies of 1st neuron – DRG (DRG = dorsal root ganglion)

ƒ  Cell bodies of 2nd neuron – lower medulla

ƒ  Cell bodies of 3rd neuron – thalamus (VPL = ventral posterolateral nucleus of thalamus)

ƒ  Fibers of 2nd neuron cross at lower part of medulla

ƒ  From VPL, it goes to somatosensory cortex in to the postcentral gyrus

ƒ  Lesion of the dorsal column: loss of two point discrimination, joint position sense, vibratory and pressure sensation; astereognosis – loss of ability to identify the characteristic of an objects; diagnosis (Dx): Romberg’s sign (patients sway when they close their eyes) and vibratory sensation by 128 Hz tuning fork (If patient has cerebellar damage, patient will sway even with their eyes open)

ƒ  Fibers of 2nd neurons must cross midline in both (DC and SpTh) sensory systems

ƒ  Anterolateral spinothelamic tract system: three neurons

ƒ  Pain, temperature (temp), and crude touch sensation from the extremities and trunk

ƒ  Cell bodies of 1st neuron – DRG

ƒ  Cell bodies of 2nd neuron – dorsal horn gray matter

ƒ  Cell bodies of 3rd neuron – thalamus (VPL)

ƒ  Fibers of 2nd neuron cross at spinal cord

ƒ  Because the pain and temp information crosses almost as soon as it enters the SC, any unilateral lesion of the SpTh in the SC or brain stem will result in a contralateral loss of pain and temp

ƒ  SpTh fibers run closely to the SC and can affect 1st in SC cavitations (Syringomyelia). Cavitations usually occur at cervical level so bilateral loss of pain and temp in UL occurs first.

ƒ  Descending hypothalamic fibers run with SpTh without crossing at brain stem therefore any lesion of SC above T2 produces Hornor’s syndrome (ipsilateral)

ƒ  Amyotrophic lateral sclerosis (ALS, Lou Gehrig’s disease) is a pure motor system disease and affects both UMN and LMN and typically begins at cervical level of spinal cord. It occurs due to mutation in superoxide dismutase gene. Increased levels of glutamate is seen in a patient with ALS. Rulizole is currently the only FDA-approved drug for ALS (see figure below).

ƒ  Brain stem: home of nine cranial nerves

ƒ  Midbrain – 3rd and 4th (4th is the only CN that exit from dorsal brain stem)

ƒ  Pons – 5th, 6th, 7th, 8th

ƒ  Medulla – 9th, 10th, 12th

ƒ  Motor nuclei of CN situated medially and sensory nuclei situated lateral to motor nuclei

ƒ   Pure motor CN – 3, 4, 6, 11, 12

ƒ  Pure sensory CN – 1, 2, 8

ƒ  Mixed CN (both motor and sensory function) – 5, 7, 9, 10

ƒ  Lesion in brain stem: loss occurs on contralateral side of any three long tracks (one motor and two sensory), Hornor’s syndrome (always ipsilateral) and ipsilateral CN lesion

ƒ  Medial longitudinal fasciculus (MLF) fiber bundle is a center for horizontal gaze connect vestibular nuclei and nuclei of CN-3, 4, 6

ƒ  Lesion of MLF leads to disrupt vestibule-occular reflex

ƒ  MLF is located in pons and midbrain in midline

ƒ  Solitary nucleus (7, 9, 10) – taste and visceral sensation

ƒ  Nucleus ambiguus (9, 10) – motorneurons (muscles of soft palate, larynx, pharynx, and upper esophagus)

ƒ  Dorsal motor nucleus of CN-10 – visceral motorneurons (major parasympathetic nucleus of the brain stem; viscera of thorax, foregut, and midgut)

ƒ  Midbrain: superior colliculus (vertical gaze) and inferior colliculus

ƒ  (auditory information – lateral lemniscus)

ƒ  Two vertebral arteries joined to form basilary artery

ƒ  Labyrinthine artery – a branch of basilar artery, supplies inner ear

ƒ  At rostral end of midbrain, the basilary artery divides into a pair of posterior cerebral arteries

ƒ  How will you identify all different syndromes on exam? – By looking at involvement of different cranial nerves. Involvement of CN-12 (medial medullary syndrome); CN-9, 10 (lateral medullary syndrome); CN-7, 8 (lateral pontine syndrome); CN-6 (medial pontine syndrome); and CN-3 (medial midbrain syndrome)

„  Pontocerebellar angle syndrome: caused by acoustic neuroma (Schwannoma) of CN-8 – absence of long tracts signs indicates that the lesion must be outside of brain

„  Parinaud syndrome: pineal gland tumor compressing superior colliculus. The most common sign is paralysis of upward (vertical) gaze (sunset sign) combined with bilateral pupillary abnormality

ƒ  High frequency sounds – base of cochlea

ƒ  Low frequency sounds – apex of cochlea

„  Vestibular System

ƒ  Urticle and saccule: linear acceleration – positional changes in the head relative to gravity

ƒ  Ampullary crest: angular acceleration – results from circular

ƒ  movement of head

ƒ  Head turns right leads to both eyes move left

„  Nystagmus: unilateral vestibular nerve or nuclei lesion produce nystagmus

9. Caloric Test

ƒ  Pouring cool water (mimic nerve lesion) into ear – nystagmus opposite side

ƒ  Pouring warm water (mimic nerve stimulation) into ear – nystagmus same side

10. Horizontal Gaze

So if the left frontal eye field is stimulated, activation of the pontine gaze center occurs on right and saccadic horizontal eye movements of both eyes occur to the right.

ƒ  Left frontal eye field lesion – both eyes can’t look to the right (but slow drift occurs to the left)

ƒ  Left MLF lesion – left eye can’t