Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Approach to the Patient with Weakness
Document related concepts
Transcript
Approach to the Patient with Weakness What are clinical features that might lead you to believe that weakness is peripheral? Why is it important to localize within the peripheral nervous system? Localization within the Peripheral Nervous system Peripheral Nerve/ Axon Neuromuscular Junction Cell Body Muscle Weakness in Motor Neuron Disease Distribution Muscle Tone Variable but asymmetric at onset Hypotonic/Flaccid* Sensory Loss No Reflexes Hyporeflexic* Other Features Atrophy, fasciculations, cramping * Amyotrophic lateral sclerosis (ALS) and some related disorders affect both the motor neuron AND the corticospinal tracts, so patients have BOTH upper and lower motor neuron signs. In addition to the above features, these patients may have spasticity and hyperreflexia. Examples of Motor Neuron Disease • Congenital – Spinal Muscular Atrophy (SMA) - Types 1(most severe)-4(adult onset) • Autosomal recessive: Survival motor neuron (SMN) gene (5q13) • Amyotrophic Lateral Sclerosis – Neurodegenerative disease affecting motor neurons of the anterior horn (LMN signs) and the motor cortex (UMN signs) – Sporadic (90-95%) and hereditary (5-10%) • Most common genetic form is autosomal dominant – Most common genes: C9ORF72 (9p21) and Superoxide dismutase (SOD) 1 (21q22) • Infectious – Poliovirus - Enterovirus eradicated in the U.S. • Other enteroviruses can cause similar disease - Enterovirus 70 and 71 – West Nile - Mosquito borne flavivirus • Post Radiation - Years after para-aortic radiation Weakness in Peripheral Nerve Disease Distribution Distal > Proximal Muscle Tone Hypotonic Sensory Loss Yes Reflexes Hyporeflexic Other Features Distal atrophy over time, paresthesias/pain Examples of Peripheral Nerve Disease •Trauma - Especially entrapment neuropathy • Axonal – Systemic illness • DM, uremia, cirrhosis, SLE, amyloidosis – Toxic • EtOH, heavy metals • Meds - Chemo (platinum, taxanes) – Nutrition • B12, folate, B6 – Infection • HIV, Herpes, leprosy • Demyelinating – Hereditary • Forms of Charcot-Marie Tooth – Guillian-Barre (AIDP) • Preceding illness – e.g. Campylobactor • Ascending weakness • No reflexes – CIDP - Chronic form – Infectious – CMV, Lyme, Cryoglobulinemia, HIV, Diptheria Weakness in Neuromuscular Junction Disease Distribution Proximal>Distal, Bulbar Muscle Tone Normal Sensory Loss No Reflexes Normal to hypo, may facilitate with repeat testing Fatigability Other Features Examples of Neuromuscular Junction Disease • Myasthenia Gravis – Postsynaptic autoimmune disease • Antibodies to ACh receptors or MuSK – Sometimes associated with thymoma • Lambert-Eaton Myasthenic Syndrome (LEMS) – Presynaptic autoimmune disease • Antibodies to voltage gated calcium channels – Often associated with small cell lung cancer • Botulism • Toxic – Organophosphates, curare, black widow venom, some snake venom, aquatic neurotoxins (cone snail, stone fish) Weakness in Muscle Disease Distribution Proximal > Distal Muscle Tone Normal Sensory Loss No Reflexes Normal Other Features Sometimes myalgia Examples of Muscle Disease • Hereditary – Duchenne/Becker muscular dystrophy • X-linked - Dystrophin gene • Duchenne (more severe) - reading frame disrupted, Becker (less severe) reading frame preserved – Mitochondrial disease • Inflammatory – Dermatomyositis • Skin change - Gottron’s papules, heliotrope • Higher incidence of malignancy – Polymyositis • Critical Illness Myopathy • Toxic – Statins, glucocorticoids Peripheral Nervous System Weakness Motor Neuron Peripheral Nerve Neuromuscular Junction Muscle Distribution Variable Typically Distal Proximal, Bulbar Proximal Muscle Tone Sensory Loss No Yes No No Reflexes If demyelinating May be facilitated or severe with repeat testing axonal large fiber Paresthesias Sometimes myalgia Other Features Fasciculations, cramping Fatiguability May be down if very weak
