Nerves and neuropathy

Nerves and Neuropathy Janice Wiesman M.D. Adjunct Assistant Professor of Neurology Boston University School of Medicine

What is a nerve? • A nerve is a cable-like bundle of axons that runs between the spinal cord and the periphery • Axons transmit information by an electrical current that runs along the axon like a wire in your home • The axons are each surrounded by a fatty coating, called myelin, that acts like insulation on a wire

What is an axon? • An axon is the arm-like extension of a nerve cell (neurons) • There are motor, sensory and autonomic neurons which send out axons • The neurons are located in or near the End that
contacts the
muscle or skin

Motor Axons (to muscle) • Motor axons run from the motor neuron cell body in the spinal cord via nerves to contact a muscle cell • When the motor neuron fires an electrical impulse, the impulse races down the axon and the end of the axon releases a chemical, called a neurotransmitter, that causes the muscle cell to contract. Sensory Axons (from skin) • Sensory axons bring information from the skin and organs up to the spinal cord so we can feel, hear, taste, smell and see • The sensory neuron sits just outside the spinal cord and sends one long axon out to the skin and sends one short axon into the spinal cord • The cells bodies that make these axons sit in the spinal cord and in brainstem and send out axons that contact – Salivary glands in the mouth – Tear glands in the eye – Muscle in the walls of blood vessels – Muscle in the walls of the stomach and What is Neuropathy? • Neuropathy is a general term meaning damage to a nerve • One nerve = mononeuropathy – Example carpal tunnel syndrome • Many nerves = polyneuropathy – Also called peripheral neuropathy Nerve Damage in amyloidosis • Seen in most types – Primary (AL) – Inherited • TTR – also called Familial Amyloid Polyneuropathy • Gelsolin • ILE122 (though not common) – Not typically seen • AA amyloid • Focal amyloid Nerve Damage in Amyloidosis • Can be one nerve – Carpal tunnel syndrome • Can be multiple (but not all) nerves • Can be generalized disorder of nerves – Amyloid polyneuropathy = peripheral Amyloid Polyneuropathy • Axonal, length-dependent, symmetrical, dying- – Axon itself is damaged • Compression • Metabolic component – Longest nerves affected first – why? – Symmetrical – The nerve degenerates from the end, upward – Thin axons affected first (pain and autonomic) – Thick axons affected later (to muscle) Symptoms of Polyneuropathy • Same in amyloid as in neuropathy due to diabetes, kidney failure or alcohol use • Start in feet, slowly climbs up the legs. When the symptoms are at knee level may have symptoms in the hands Symptoms of Polyneuropathy • Tingling, numbness, burning, feeling cold, feeling like walking on cotton/something in your shoe • Often feel worse at night – Off your feet – Not distracted Symptoms of Polyneuropathy • Why does it feel numb and painful at the – Different axons mediate different sensations – Thin axons mediate pain sensation • When damaged, they fire – brain "feels" it as pain – Thick axons mediate touch and pressure • When damaged, do not transmit information to the brain – so brain does not "feel" touch Diagnosis of Amyloid • History • Examination • Nerve Conduction Studies • Electromyography (EMG) • Blood work • Nerve biopsy (not common) • No other cause Polyneuropathy related to the organ damage caused by amyloidosis • Kidney dysfunction • Malnutrition Polyneuropathy related to other medical problems – Good sugar control is key • Regular alcohol consumption – Don't hit your nerves when they are down – Ask your doctor Polyneuropathy related to treatment of amyloidosis • Not an issue with inherited forms • Primary amyloidosis – Chemotherapy • Revlimid (derived from thalidomide) • Velcade • Platinum medications • Typically improves after treatment stopped – 6-12 months typical • NOT – dexamethasone or Melphalan If I am treated will my nerves • Maybe • Nerves regrow best in people who are young and otherwise healthy • Nerves grow back slowly Treatment of Polyneuropathy • First ask – Do I Need To Be Treated? – Is underlying disease being treated? – No treatment to make nerves grow back – Treatment is symptomatic • Crazy-making: Yes or No?? Symptomatic Treatment of • Without Medication – Foot rub or warm water foot massage before – Acupuncture (but check with your doctor regarding risk of infection!!!) Symptomatic Treatment • Topical Medication – Lidoderm patch – topical anesthetic – Solarcaine – topical anesthetic – Capsacin • causes release of Substance P (causes pain) • initially increases pain • must be used 2-3 times/day Symptomatic Treatment • Anti-seizure medications – Lyrica (pre-gabalin) – Neurontin (gabapentin) – others • Antidepressants – Cymbalta (duloxetine) – "tricyclic antidepressants" like Elavil – not typically used in • Anti-inflammatory – Aspirin-like drugs – Tylenol – Extended release pills or patch Treatments for severe pain – Extended release pill or patch • Nerve stimulation (TENS) • Spinal cord stimulation – Very invasive, risk of infection Symptoms of Autonomic • Dry eyes and mouth – Nerves to the glands are damaged • Trouble accommodating to bright light – Autonomic nerves control how constriction of the pupil in the eye • Lightheadedness when standing – Blood vessels do not constrict when you stand up – Heart rate does not increase when you stand up • Diarrhea • Constipation • Erectile dysfunction • Talk to your doctor about symptomatic treatment for

$70 for one month A word about foot care • Foot care is important • If you can't feel your feet you can't feel cuts or sores that can become infected. • Foot care tips – Look between and under your toes every day – Wear soft, well fitting shoes – Do not walk barefoot, particularly outside – Keep feet soft and well moisturized – Have nails filed rather than cut • A podiatrist or specialized pedicurist can help • Don't cut your own nails • We want you have all 10 toes, all of the time! A word about muscle disease • Steroids, such as prednisone and dexamethasone can cause wasting and weakness of muscles. • This typically affects muscles that are closest to • Trouble walking up stairs or getting out of a chair • Muscle mass and strength typically return to normal after treatment ends. Carpal tunnel syndrome (CTS) • Common in primary and TTR Amyloidosis • The median nerve runs down from the neck into the hand • At the wrist, the nerve runs under a band of connective tissue that encircles the wrist • Amyloid deposits in the connective tissue and compresses the nerve Carpal Tunnel Syndrome • There are 3 main nerves that go into the hand • The Median nerve runs under the transverse carpal ligament and can be compressed in amyloidosis because amyloid deposits in the ligament and thickens it. • The Radial and Ulnar nerves run over the ligament and are not compressed. Carpal Tunnel Syndrome Carpal Tunnel Syndrome • Tingling, pain ,numbness in the thumb, forefinger and middle finger • Weakness of the thumb and of grip • Trouble opening jars and buttoning • Worse at night, with driving, typing • Ergonomic adjustment • Wrist brace • Local injection of steroid • Surgery – Always make sure the surgeon sends a sample of the connective tissue band to pathology!! What you can do for healthy 1. CUT DOWN ON ALCOHOL – IT IS DIRECTLY TOXIC TO NERVES 2. STOP SMOKING – WITH EVERY PUFF YOU CAUSE CONSTRICTION OF THE BLOOD VESSELS THAT NOURISH NERVES 3. EAT A LOT OF FRUITS AND VEGETABLES, ESPECIALLY DARK GREEN LEAFY VEGETABLES WHICH CONTAIN B VITAMINS (but not if you are taking coumadin) 4. MUSCLES DEPEND ON THEIR NERVE SUPPLY TO STAY HEALTHY – USE THEM BOTH • Healthy Nerves pamphlet on ASG website • Boston University Amyloid Treatment and Research Website – Podcasts – Healthy Nerves pamphlet



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