Resumo Breve
O vídeo discute a polineuropatia, uma condição que envolve lesões em múltiplas fibras nervosas periféricas. Os pontos principais incluem:
- A polineuropatia é frequentemente causada por diabetes e alcoolismo.
- Ela pode resultar em perda de sensibilidade e fraqueza nos membros, afetando principalmente os nervos motores e sensoriais.
- O diagnóstico é feito através de estudos de condução nervosa.
A polineuropatia é uma desordem que envolve danos a várias fibras nervosas periféricas, comumente afetando os nervos distais. A manifestação clássica inclui uma sensação simétrica de queimação ou perda de sensibilidade. Entre as causas comuns, destacam-se o álcool e a diabetes, enquanto causas raras incluem a doença de Charcot-Marie-Tooth.
O sistema nervoso é dividido em central e periférico. O sistema nervoso central é composto pelo cérebro e pela medula espinhal, enquanto o sistema nervoso periférico conecta o central aos órgãos, membros e pele. As fibras nervosas periféricas variam em tamanho e incluem nervos motores, sensoriais e autonômicos.
As fibras nervosas podem ser mielinizadas, que são mais rápidas na transmissão de sinais, ou não mielinizadas, que são mais lentas. As fibras mielinizadas estão protegidas por uma bainha de mielina que permite uma rápida condução do impulso nervoso, enquanto as não mielinizadas são mais suscetíveis a danos.
Na polineuropatia, existem dois padrões de lesão: perda axonal e desmielinização. A perda axonal resulta em menos neurônios e sinais de nervos mais fracos, enquanto a desmielinização causa uma desaceleração nos sinais. A apresentação clínica varia de acordo com o tipo de lesão, afetando fibras motoras, sensoriais ou autonômicas.
Na polineuropatia axonal, as fibras nervosas mais longas são afetadas primeiro, começando pelos pés e subindo. Este tipo de lesão resulta em dormência e sensação de queimação, com eventual fraqueza muscular. Em contraste, lesões desmielinizantes tendem a afetar primeiro os nervos motores, apresentando mais fraqueza do que alterações sensoriais.
As causas da polineuropatia podem ser agrupadas conforme o mecanismo da lesão, com a perda axonal sendo a mais comum, ocorrendo frequentemente devido à diabetes e ao álcool. Outras causas incluem quimioterapia, hipotiroidismo e deficiência de vitamina B12.
A desmielinização, embora rara, pode ocorrer em condições como a síndrome de Guillain-Barré, que causa fraqueza simétrica ascendente e é tratada urgentemente com imunoglobulinas intravenosas. A polineuropatia inflamatória crônica é uma forma diferente que se desenvolve lentamente ao longo do tempo.
O diagnóstico de polineuropatia envolve testes laboratoriais e estudos de condução nervosa para determinar se a condição é devida a lesão axonal ou desmielinizante. Os achados nos estudos podem indicar se a polineuropatia é causada por danos a neurônios ou a desmielinização, influenciando o tratamento subsequente.
Em resumo, a polineuropatia pode ser dividida em perda axonal ou desmielinizante, sendo a perda axonal mais comum, frequentemente ligada à diabetes e ao alcoolismo. O estudo da condução nervosa é o padrão ouro para investigação, levando a diagnósticos mais precisos e tratamento adequado.
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Transcrição
Transcrição completa de “Approach to Polyneuropathy - causes, pathophysiology, investigations”. Clique em uma marcação de tempo para abrir o vídeo naquele momento. Precisa de outro vídeo? Use o gerador de transcrição do YouTube.
0:05 polyneuropathy is a disorder that involves damage to multiple peripheral nerve fibers with the distal nerves usually affected most predominantly and so the classical presentation is a symmetric distal burning or loss of sensation common causes include alcohol and diabetes and then you have rare causes such as charcoal mary tooth disease the body's nervous system is divided into the central and peripheral nervous system the central nervous system is our brain and spinal cord the peripheral nervous system is a division of the nervous system that contains all the nerves outside the central nervous system its main function is to connect the central nervous system with the organs
0:51 the limbs and the skin your peripheral nerve fibers come in different sizes from largest to smallest you have the motor nerves which are myelinated sensory nerves which can be myelinated or unmyelinated and then you have the autonomic nerves which are usually the smallest and are unmyelinated or lightly myelinated myelinated nerve fibers means that they contain or are surrounded by myelin sheath myelin allows for rapid transfer of signals rapid conduction unmyelinated fibers are slower the peripheral nerves are not as well protected as the central nervous system and are susceptible to a variety of
1:38 toxic inflammatory hereditary infectious things that can lead to polyneuropathy polyneuropathy can affect the peripheral motor nerve fibers the sensory nerve fibers or both as well as the autonomic nerve fibers there are two patterns of injury in peripheral neuropathy or polyneuropathy and these are axonal loss or demyelination axonal loss implies that there are less number of neurons because they are damaged and as a consequence the nerve fiber will send a weaker signal demyelination means loss of myelin and as we know myelinated neurons allow
2:24 for faster signals therefore demyelination causes slowing of signals these two patterns of injury differ in clinical presentation polyneuropathy can affect motor sensory or autonomic nerve fibers axonal polyneuropathy affects the longer nerve fibers first starting distally and then progresses proximally it affects sensory nerve fibers before the motor nerve fibers the longer nerve fibers are the ones that supply your legs the hands are affected once the neuropathy is above the knees typically now the majority of polyneuropathy is axonal
3:11 sensory nerve injury causes symmetrical numbness burning sensation pins and needles of the distal lower limbs this will progressively ascend up the lower limbs and affect feet before hands eventually the motor nerve fibers are also affected causing weakness and atrophy clinically you also get a reduced deep tendon reflex in demyelinating injury typically the large nerve fibers are affected first which are your motor nerves and this will present with weakness more than sensory changes eventually however most patients will complain of sensory changes
4:00 polyneuropathy is a disorder that involves damage to multiple peripheral nerve fibers differential diagnosis for polyneuropathy include other peripheral neuropathies these include radiculopathy which is injury or damage to the nerve root and this causes sensation deficit in a specific dermatomal pattern and weakness in a specific myotome there's also plexopathy which is damaged to a nerve plexus such as a brachial plexus a type of peripheral neuropathy is also a mononeuropathy which is damaged to a single peripheral nerve such as in carpal tunnel syndrome
4:47 another differential is monouridis multiplex which is damaged to multiple nerves in an asymmetrical distribution so for example in carpal tunnel as well as if someone has a foot drop the causes of polyneuropathy can be divided based on the mechanism of injury we we talked about axonal loss or demyelination axonal loss is the most common cause of polyneuropathy and include the two most important causes diabetes and alcoholism other causes include chemotherapy hypothyroidism vitamin b12 deficiency hiv infection other rare causes include uremic
5:33 polyneuropathy paraprotinemia critical illness polyneuropathy and paraneoplastic demyelination is a rare cause of polyneuropathy and these include guillain-barre syndrome chronic inflammatory demyelinating polyneuropathy and charcoal mary tooth disease guillain-barre is an acute peripheral demyelinating condition which also has an axonal variant it is associated with a past capital bacteria infection viral infection as well as vaccination it causes a symmetrical ascending weakness can also affect the respiratory muscles
6:20 diagnosis is with a lumbar puncture which shows elevated proteins and it is treated urgently with intravenous immunoglobulins while guillain-barre syndrome is an acute form and often patients do recover from this demyelinating disease they could progress and develop chronic inflammatory demyelinating polyneuropathy chronic inflammatory demanding polyneuropathy is different because it's chronic and usually slow slowly progressive patients eventually are wheelchair bound or bed bound charcoal mary tooth disease is a hereditary sensory motor polyneuropathy which also has an axonal variant
7:05 there is a gene duplication of pnp and chromosome 17. classic features of charcoal mary tooth include symmetric distal sensory and motor polyneuropathy pescavis hammertoe foot drop calf muscle atrophy with an inverted champagne bottle appearance and hand muscle wasting investigations for polyneuropathy includes performing blood tests and specific tests for all the differential diagnoses we talked about but ultimately a nerve conduction study is used to determine whether the polyneuropathy is due to an
7:52 axonal or demyelinating injury axonal loss implies that there are less number of neurons because they are damaged this causes a weaker signal to be sent and manifests as a reduction in amplitude on the nerve conduction study demyelination means loss of myelin and as we know myelinated neurons allow for faster signals conduction therefore demyelination causes slowing or a reduced velocity on nerve conduction study so in summary polyneuropathy can be divided into either axonal loss or demyelinating and there are many differential diagnoses but
8:38 an axonal loss is more common and is due to diabetes and alcohol most commonly the gold standard investigation would be a nerve conduction study and then further investigations to determine the actual etiology thank you for watching i hope you enjoyed this video [Music] you
