NEUROLOGY. BRIEF REVIEW

Parkinson’s disease	Degenerative disorder of CNS associated with Lewis bodies and depigmentation of the substantia nigra pars compacta. Tremor at rest, pill-rolling tremor, cogwheel rigidity, akinesia, and postural instability.
Hemibalismus	Sudden, wild flailing of one arm (sometime one leg). Characterized by Subthalamic nucleus lesion. Loss of inhibition of thalamus through globus pallidus.
Huntington’s disease	Autosomal dominant trinucleotide (CAG) repeats disorder. Chorea, aggression, depression, and dementia. Atrophy of striatal nuclei (main inhibitor of movement). Caudate loses ACh and GABA.
Chorea	Sudden, jerky, purposeless movement. Basal ganglia lesion e.g. Huntington’s disease.
Athetosis	Slow, writing movements, especially of fingers. Basal ganglia lesion.
Myoclonus	Sudden, brief muscle contraction. Jerks, hiccups.
Dystonia	Sustained, involuntary muscle contractions. Writer’s cramps.

 First aid for USMLE Step 1. 2011.

Intracranial hemorrhage

Epidural hematoma	Rupture of the middle meningeal artery, often secondary of temporal bone fracture. Lucid interval. Rapid expansion under systemic arterial pressure produce transtentorial Herniation, CN III palsy	CT shows= biconvex disk, not crossing suture lines, but can cross falx and tentorium
Subdural hematoma	Rupture of bridging veins, slow venous bleeding (less pressure= hematoma develop overtime) with delayed onset of symptoms. Seen: elderly, alcoholics, blunt trauma, and shaken baby. Predisposing factor: brain atrophy, shaking, whiplash.	Crescent-shaped hemorrhage that crosses suture lines. Gyri are preserved, since pressure is distributed equally. Cannot cross falx, tentorium.
Subarachnoid hemorrhage	Rupture of aneurysm or arteriovenuos malformation. Patients complain of “worst headache of my life”. Bloody or yellow spinal tap. 2-3 days afterward.
Parenchymal hematoma	Caused: hypertension, amyloid angiopathy, diabetes mellitus, and tumor. Typically occurs in basal ganglia and internal capsule.

                                                  BRAIN LESIONS

Area of lesion	Consequence
Amygdale(bilateral)	Klüver-Bucy syndrome (hyperorality, hypersexuality, disinhibited behavior)
Frontal lobe	Disinhibition and deficit in concentration, orientation, and judgment; may have reemergence of primitive reflexes
Right parietal lobe	Spatial neglect syndrome (agnosia of the contralateral side of the world)
Reticular activating system (midbrain)	Reduce levels of arousal and wakefulness
Mamillary bodies (bilateral)	Wernicke-Korsakoff syndrome
Basal ganglia	Tremor at rest, chorea, or athetosis
Cerebellar hemisphere	Intention tremor, limb ataxia; damage of cerebellum result in ipsilateral deficit, fall toward side of lesion
Cerebellar vermis	Truncal ataxia, dysarthria
Subthalamic nucleus	Contralateral hemibalismus
Hippocampus	Anterograde amnesia
Paramedian pontine reticula formation	Eyes look away from site of lesion
Frontal eyes fields	Eyes look toward lesion

SKIN DISORDERS (PART II)

Pemphigus vulgaris	Potentially fatal autoimmune skin disorder with IgG autoantibody against desmosome. Achantolysis (intraepidermal bullae involving skin and oral mucosa). Nikolsky’s sign positive (separation of epidermis upon manual stroking the skin).
Bullous pemphigoid	Autoimmune disorder with IgG antibody against hemidesmosomes. Eosinophils within blister. Similar but less severe than Pemphigus vulgaris. Affects skin but spares the oral mucosa. Nikolsky’s sign negative.
Dermatitis herpetiformis	Pruritic papules and vesicles. Associated with celiac disease.
Erythema multiforme	Associated with infection (Mycoplasma pneumoniae, HSV), drugs (sulfas, β lactams, phenytoin), cancer and autoimmune diseases. Presents with multiples types of lesions.
Stevens-Johnson syndrome	Fever, bulla formation and necrosis, sloughing of skin, and high mortality rate. Associated with adverse drug reaction. Toxic epidermal necrolysis (more severe form of S-J synd.)
Lichen planus	Pruritic, purple polygonal papules. Associated with hepatitis C.
Actinic keratosis	Premalignant lesions caused by sun exposure. Small, rough, erythemotous or brownish papules. Risk of carcinoma is proportional to epithelial dysplasia
Achantosis nigricans	Hyperplasia of stratum spinosum, associated with hyperinsulinemias (Cushing diseases, diabetes) and visceral malignancy.
Erythema nodosum	Inflammatory lesion of subcutaneous fat, usually on anterior shins. Associated with coccidioidomycosis, histoplasmosis, TB, leprosies. Streptococcal infections and sarcoidosis.
Pityriasis rosea	Multiple papular eruptions, remits spontaneously. “Herald patch” followed days late by “Christmas tree” distributions.
Strawberry hemangioma	First few weeks of life. Grows rapidly and regresses spontaneously at 5-8 years of age.
Cherry hemangioma	Appears in 30s-40s, does not regress.

Bibliography:  First aid for USMLE step 1, 2011

SKIN DISORDERS

Verrucae	Warts. Soft, tan-colored, cauliflower like lesion. Epidermal hyperplasia, hyperkeratosis, koilocytosis. Verruca vulgaris on hands Condyloma acuminatum on genitals (caused by HPV)
Nevocellular nevus	Common mole. Benign.
Urticaria	Hives. Intensely pruritic wheals that form after mast cell degranulation
Ephelis	Freckle. Normal number of melanocytes, ↑ melanin pigment.
Atopic dermatitis(eczema)	Pruritic eruption, commonly in skin flexure. Associated with other Atopic diseases.
Allergic contact dermatitis	Type IV hypersensitivity reaction. Lesions occur at site of contact
Psoriasis	Papules and plaques with silvery scarling, especially on knees and elbows. Achantosis with parakeratotic scaling. ↑ Stratum spinosum, ↓ stratum granulosum. Auspitz sign (bleeding spots when scales are scraped off). Nail pitting, psoriatic arthritis.
Seborrheic keratosis	Flat, greasy , pigmented squamous epithelial proliferation with keratin-filled cyst. Looks “pasted on”. Common benign neoplasm of older persons. Signs of Leser-Trelat=sudden appearance of multiples seborrheic keratoses indicating an underlying malignancy (GI, Lymphoid).
Albinism	Normal melanocytes number with ↓ melanin production due to ↓ tyrosinase activity.
Vitiligo	Irregular areas of complete depigmentation. Caused by ↓melanocytes.
Melasma(chloasma)	Hyperpigmentation associated with pregnancy and OCP use.
Impetigo	Very superficial skin infection. Usually from S. aureus and S. pyogenes. Highly contagious. Honey-colored crusting.
Cellulites	Acute, painful spreading infection of dermis and subcutaneous tissues. Usually from S. pyogenes and S. aureus.
Necrotizing fasciitis	Deeper tissue injury, usually from anaerobic bacteria and S. pyogenes. “Flesh eating bacteria”.
Staphylococcal scalded skin syndrome	Exotoxin destroys keratinocytes attachment in the stratum granulosum only. Fever and generalized erythemotous rash with sloughing of the upper layers of epidermis. Seen in newborns and children..
Hairy leukoplakia	White, painless plaque on the tongue, that can’t be scraped off. EBV mediated. Occur in the HIV (+) patients.

LAB VALUES IN BONE DISORDERS

	Serum Ca	Phosphate	ALP	PTH	Comments
Osteoporosis	Normal	Normal	Normal	Normal	↓ bone mass
Osteopetrosis	Normal	Normal	Normal	Normal	Thickened, dense bone
Osteomalacia/rickets	↓	↓	Normal	↑	Soft bones
Osteitis fibrosa cystica	↑	↓	↑	↑	“Brown tumors”
Paget’s disease	Normal	Normal	↑	Normal	Abnormal bone architecture