Clinical References



Clinical References





General Neurology


NEUROANATOMY



  • Cerebral cortex: convoluted sheet of neural tissue at the rostral pole of the neuraxis; functionally includes the hippocampus



  • Cerebellum:



    • Movement coordination, sensory-motor integration, balance, modulation of affect and cognition


    • Divided into lateral hemispheres, medial vermis, flocculonodular lobe, and deep cerebellar nuclei (dentate, interpositus, fastigial, and vestibular)


    • Blood supply is from the superior cerebellar artery (SCA), anterior inferior cerebellar artery (AICA), posterior inferior cerebellar artery (PICA)


  • Basal ganglia: caudate, putamen, globus pallidus, nucleus accumbens, subthalamic nucleus and substantia nigra



    • Motor control, cognition, emotion, learning


    • Direct pathway (stimulatory): → globus pallidus interna (GPi) and substantia nigra pars reticulata (SNr) → thalamus → cortex, D1-receptor mediated


    • Indirect pathway (inhibitory): → globus pallidus externa (GPe) → STN → GPi and SNr → thalamus → cortex, D2-receptor mediated


    • Blood supply is mainly from the medial cerebral artery (MCA) (lenticulostriate)


  • Brainstem: cranial nerve nuclei, midbrain, pons, medulla



    • Integrative functions (cardiovascular, respiratory, pain sensitivity, alertness, sleep-wake cycles)


    • Blood supply is from the direct branches off the basilar, vertebral arteries








TABLE 6-1 Regions of the Cerebral Cortex

Function

Input

Blood Supply


Occipital lobe

Visual

LGN thalamus

PCA


Temporal lobe

Visual form perception (lateral, inferior)
Audition and language (superior)
Memory (medial)

MGN thalamus, occipital and frontal cortices

MCA


Parietal lobe

Visual motion, space perception, somatosensation, polysensory processing, visuospatial attention, movement planning, language (dominant hemisphere)

VP and pulvinar thalamus, occipital and frontal cortices

MCA


Frontal lobe

Movement planning and execution, memory, executive function, awareness, insight, judgment
Speech (lateral, dominant hemisphere)

VL and medial dorsal thalamus

MCA, ACA


Limbic system*

Memory, emotion, motivation, visceral processing (autonomic, gustatory, endocrine)

Papez circuit†

ACA, MCA


* The limbic system consists of the hippocampus, amygdala, septum, cingulate, orbital, insula, hypothalamus, and mamillary bodies.

† Papez circuit: cingulate → parahippocampal gyrus → hippocampus → fornix → mammillary bodies → anterior thalamus → cingulate.


ACA, anterior cerebral artery; MCA, middle cerebral artery; LGN, lateral geniculate nucleus; MGN, medial geniculate nucleus; PCA, posterior cerebral artery; VL, ventral lateral; VP, ventral posterior.









TABLE 6-2 Diffuse Modulatory Neurotransmitter Systems







































Neurotransmitter

Synthesis Location

Receptors or CNS Pathways

Functions (Example of Pathology)


Cholinergic (ACh)

Basal nucleus of Meynert, medial septal nucleus

M1; brainstem, neocortex, and hippocampus

Learning, short-term memory, arousal, reward (delirium)


Dopaminergic (DA)

Substantia nigra, ventral tegmental area

Mesocortical (dorsolateral prefrontal cortex)

Cognition, motivation (schizophrenia)


Mesolimbic (nucleus accumbens)

Reward (addiction)


Nigrostriatal (basal ganglia)

Motor (Parkinson’s disease)


Tuberoinfundibular (hypothalamus)

Prolactin secretion, endocrine function


Noradrenergic (NE)

Locus ceruleus, lateral tegmental area

Receptors diffusely throughout CNS

Arousal, reward, attention (depression, ADHD)


Serotonergic (5HT)

Raphe nuclei

Receptors diffusely throughout CNS

Mood, satiety, temperature, sleep, pain sensitivity (depression, chronic pain symptoms)


ADHD, attention-deficit hyperactivity disorder; CNS, central nervous system.




NEUROLOGIC EXAMINATION FINDINGS

See page 7 for approach to the examination.


Abnormal Speech



  • Dysarthria: pure motor dysfunction of larynx or tongue


  • Aphasia: dysfunction in repetition, comprehension, or fluency








TABLE 6-3 Types of Abnormal Speech






































Type of Aphasia

Repetition

Comprehension

Fluency


Broca’s

Impaired

Intact

Nonfluent


Wernicke’s

Impaired

Impaired

Fluent


Conduction

Impaired

Intact

Fluent


Global

Impaired

Impaired

Nonfluent


Transcortical, sensory

Intact

Impaired

Fluent


Transcortical, motor

Intact

Intact

Nonfluent



Abnormal Movements



  • Athetosis: slow, writhing continuous movements; often brought out by moving other body parts


  • Asterixis: transient lapses of limb postural control, most often caused by hepatic or renal failure


  • Chorea: involuntary, irregular, purposeless, nonrhythmic, abrupt movements that flow from one body part to another; increased by stress; caused by caudate nucleus damage from streptococcal infection (Sydenham’s chorea), Huntington’s disease, drugs, or systemic lupus erythematosus


  • Dyskinesia: abnormal involuntary movement (vs. tardive dyskinesia, which are involuntary, continuous movements clustered around the mouth and face, usually caused by long-term antipsychotic or levodopa use)


  • Dystonia: twisting movements; sustained at peak of the movement; repetitive and often progressing to prolonged abnormal postures; caused by co-contraction of agonist or antagonist muscles; focal dystonias include blepharospasm (eyelids), spasmodic torticollis (neck), oculogyric crisis (eyes), buccolingual crisis (mouth or tongue)


  • Hemiballismus: large-amplitude choreiform movements; usually from a lesion of the contralateral subthalamic nucleus


  • Myoclonus: brief, irregular movement of the muscles; cannot be controlled by effort or will (unlike tics); may be repetitive; generalized myoclonus occurs in familial disorder, subacute sclerosing panencephalitis, Creutzfeldt-Jakob disease, toxic metabolic encephalopathy


  • Tics: repetitive, stereotyped movements (motor or vocal) under some degree of voluntary control



    • Tourette’s syndrome: chronic tic disorder beginning before age 18 years; tics occur multiple times per day for more than1 year; treatment includes
      clonidine, guanfacine, antipsychotics (especially Pimozide), selective serotonin reuptake inhibitors (especially if the patient has comorbid depression or obsessive-compulsive symptoms); habit reversal therapy, and surgery (deep brain stimulation for severe refractory disease); psychostimulants may exacerbate tics


  • Tremor:



    • Resting: idiopathic; seen in Parkinson’s disease (3-6 Hz); decreases with movement; treatment: anticholinergics, dopamine agonists, amantadine, levodopa


    • Action: physiologic; postural (8-12 Hz); enhanced with nebulizers, anxiety, caffeine, endocrine disorders


    • Essential: recurrent constant tremor of the arms or head (4-8 Hz) may be kinetic or postural, autosomal dominant; improves with alcohol; treatment: propranolol, primidone, topiramate stereotactic surgery or stimulation


    • Orthostatic: appears after minutes of standing; treatment; clonazepam


    • Drug-induced: antipsychotics, antidepressants, levodopa, beta agonists, lithium, caffeine, amphetamines, steroids


NEUROLOGIC ILLNESSES


Ischemic Stroke


RISK FACTORS



  • Modifiable: hypertension (HTN), cardiac disease, hyperlipidemia, tobacco, diabetes mellitus, obstructive sleep apnea, physical inactivity, carotid artery stenosis, use of oral contraceptives (especially in smokers), drug use (cocaine, heroin, alcohol), treatable prothrombotic states (e.g., cancers, infections)


  • Nonmodifiable: Age (.55 years), race (African American, Hispanic. Caucasian), family history, prior stroke or transient ischemic attack, heritable coagulopathies


CAUSES



  • Cardioembolic: 20% (roughly 50% associated with atrial fibrillation)


  • Small vessel disease: 25%


  • Large vessel disease: 20%


  • Cryptogenic: 30%


  • Other: 5% (hypercoagulable states, dissections, arteritis, migraine or vasospasm, drug abuse)


Large Vessel Acute Stroke Syndromes



  • Middle cerebral artery (MCA): Contralateral motor and sensory loss with aphasia (dominant) or neglect (nondominant)


  • Anterior cerebral artery (ACA): unilateral → contralateral lower extremity weakness; bilateral → bilateral lower extremity weakness, bladder symptoms, abulia


  • Posterior cerebral artery (PCA): homonymous hemianopsia, memory loss, language dysfunction, hemisensory loss or hemiplegia, visual agnosia


  • Vertebral artery (VA): altered gait, dizziness, lateral medullary symptoms (Horner’s syndrome, ipsilateral ataxia, contralateral hypoalgesia, ipsilateral cranial nerve V palsy, nystagmus)



  • Unilateral ICA: amaurosis fugax, hemiparesis, hemianopsia, aphasia (dominant side), hemineglect (nondominant side), Horner’s syndrome


  • Anterior ACA or MCA: crural hemiparesis with mutism, transcortical motor aphasia (dominant side) or mood change (nondominant side)


  • Posterior MCA and PCA: hemianopia with transcortical sensory aphasia (dominant side) or neglect (nondominant side)



    • Subcortical (cortical and deep MCA branches): hemiparesis and stepwise progression


  • Watershed infarcts: ischemic infarction in a territory located at the periphery of two bordering arterial distributions


Transient Ischemic Attack



  • Symptoms: clear onset (usually ,1 min) and course (usually ,20 min; maximum, 24 hr)


  • Differential diagnosis: migraines, focal seizure, tumors, subdural hematoma (SDH), hypoglycemia, primary ear or eye disease


Hemorrhage


INTERCEREBRAL HEMORRHAGE (HEMORRHAGIC STROKE)



  • Causes: HTN (most common), aneurysm or arteriovenous malformation (AVM) rupture, trauma, coagulopathy (thrombocytopenia, liver disease, leukemia, aplastic anemia, anticoagulant or thrombolytic treatment), central nervous system (CNS) tumors (primary or metastatic), septic emboli, vasculitis, amyloid angiopathy, use of vasopressor drugs, exertion, herpes encephalitis


SUBARACHNOID HEMORRHAGE



  • Causes: trauma (most common), aneurysm, AVM, angiopathies (Marfan syndrome, polycystic kidney disease, Ehlers-Danlos), coagulopathies, venous thrombosis, allergic reaction, meningitis, herpes encephalitis, drugs (cocaine, amphetamines), brain tumors, eclampsia, vasculitis


  • Symptoms: sudden-onset, severe headache (“worst headache of my life”); brief loss of consciousness (LOC); lethargy; somnolence; meningeal signs; nausea and vomiting; focal neurologic symptoms (may be absent); HTN; retinal hemorrhages


Seizures



  • Generalized seizures: result in abnormal activity throughout the cortex; LOC; usually no aura or specific warning; may have a nonspecific prodrome



    • Generalized tonic-clonic seizures: LOC; tonic contractions followed by symmetric limb jerks followed by postictal phase; look for Todd’s paralysis (focal neurologic deficit that resolves over 36 hours)


    • Absence seizures: genetically transmitted; start in childhood and rare after puberty; spells with brief LOC (5-10 sec) with no loss of tone; also have subtle motor signs and automatisms; patients have hundreds of spells daily


    • Other generalized seizures:



      • Tonic seizures: continued muscle contraction with LOC; may lead to arrest of ventilation; may lead to a fall and drop attack


      • Clonic seizures: clonic jerking with LOC


      • Myoclonic seizures: sudden, brief, shocklike contractions; localized or generalized



      • Atonic seizures: result from loss of postural tone; lead to a fall and drop attack


  • Partial seizures: localized in one area of the brain; also called focal

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Jun 12, 2016 | Posted by in PSYCHIATRY | Comments Off on Clinical References

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