A. Nervous System Divisions

1. Central Nervous System (CNS)
2. Peripheral Nervous System (PNS)
3. Autonomic Nervous System (ANS)

B. Disease Types

1. Infectious
   1. Infection of the meninges
   2. Infection of the brain parenchyma
   3. Slow virus infections
2. Neoplastic
3. Vascular
   1. Thromboembolic stroke
   2. Atherosclerotic disease
   3. Cerebral hemorrhage
   4. Peripheral Arterial Disease (PAD)
   5. Vasculitis
   6. Intracranial Aneurysm
4. Diabetes - peripheral neuropathy
5. Inflammatory Demyelination Syndromes
   1. Multiple Sclerosis
   2. Guilliame-Barre Syndrome: peripheral nervous system - PNS
   3. Chronic inflammatory demyelinating polyneuropathy (CIDP) - PNS
6. Leukoencephalopathy [1]
   1. Structural alteration of cerebral white matter
   2. Myelin suffers the most damage
   3. Includes inflammatory and non-inflammatory (mainly toxin) forms
7. Degenerative Diseases [2]
   1. Alzheimer's Disease
   2. Parkinson's Disease
   3. Lou Gerig's Disease
   4. Prion Based Diseases [3]
8. Genetic - especially storage diseases
9. Radiculopathy (Nerve Root Disease)

C. Neurological Diagnosis

1. Precise location of lesion is extremely critical
   1. Careful history and focused physical exam
   2. Functional deficits on physical exam as clues
   3. Imaging: CT, MRI, PET, SPECT scans
2. Lumbar Puncture (Spinal Tap)
   1. Infection - rapid diagnosis is critical
   2. Tumor - caution due to mass effect, possibility of herniation
   3. Inflammation
3. Biopsy
   1. Nerve, muscle, or brain
   2. Biopsy itself produces a lesion, with possible consequences
4. Electrical Studies
   1. Nerve conduction
   2. Evoked potentials
   3. Electroencephalography (EEG)

D. Types of Lesions

1. Axonal Nerve injury
2. Demyelination
3. Astrocyte Injury
4. Oligodendrocytes
5. Ependymal Cells
6. CNS or PNS Inflammation
7. Mass effects: usually neoplastic; abscess and autoimmune also occur

E. Radiculopathy (Nerve Root Disease)

1. Increasingly common with osteoarthritis / degenerative joint disease
2. Nerve roots pass through thecal sac to neural foramina
3. Narrowing of the neural foramina can lead to root dysfunction
4. Bone spurs, disk prolapse or herniation are the most common causes of radiculopathy
5. Weakness and pain are the most common presenting symptoms
6. Commonly Affected Regions and Weakness
   1. Cervical C5, C6, and C7
   2. Lumbar L4 and L5
   3. Sacral S1
7. Sites of Weakness
   1. C5: shoulder abduction
   2. C6: elbow flexion
   3. C7: elbow extension, wrist flexion and extension, and hand grip
   4. C8: hand grip, hand intrinsic muscles
   5. L2-3: hip flexion
   6. L5-S1: hip extension and ankle plantar flexion
   7. L3-4: knee extension
   8. L4-5: knee flexion and ankle dorsiflexion

References

1. Filley CM and Kleinschmidt-DeMasters BK. 2001. NEJM. 345(6):425
2. Martin JB. 1999. NEJM. 340(25):1970
3. Prusiner SB. 2001. NEJM. 344(20):1516