Ep. 183: Nerve ultrasound

00:00:00: Welcome to EANcast, your weekly source for education, research and updates from the European Academy of Neurology.

00:00:15: Hello and welcome to EANcast, Weekly Neurology.

00:00:19: My name is Gabriela Roussin and I'm culture of the scientific panel on clinical neurophysiology.

00:00:26: Today we are discussing nerve ultrasound and topic that is rapidly transforming neuromuscular diagnostics.

00:00:33: My guest today is Professor Jakub Antczak from University Hospital in Kraków.

00:00:39: Welcome, Professor Antczak.

00:00:41: It is great to have you with us.

00:00:43: Thank you for having me.

00:00:45: Let's start from the top.

00:00:46: Why has nerve ultrasound become such an important tool in neurobascular medicine over the last decade?

00:00:54: It is because of the progress in hardware and software of the ultrasound equipment, which has been tremendous during recent years.

00:01:03: It may manifest most often in the musculoskeletal medicine where exquisite visualization of ligaments, bores, tendons and other periarticular elements is now possible and helps to establish the etiology of the disorders of the locomotor system.

00:01:20: Less popular is the use of the ultrasound to visualize the peripheral nervous system.

00:01:26: On the other hand, the body of research documenting specific changes in particular disorders of of peripheral nervous system is growing rapidly.

00:01:35: The good example is that real data were convincing enough to introduce nerve ultrasound in diagnostic guidelines issued recently by Fofors chronic inflammatory demilinating polyneuropathy, which were issued recently by the European Academy of Neurology and Peripheral Nerve System Society.

00:01:58: In my view, Ultrasound is an excellent method complementary to electrodiagnostics and I think so because since decades I am involved in electromyography conduction studies and evoke potentials.

00:02:12: I know that other colleagues can have a different approach.

00:02:15: Someone who is a radiologist or radiologist or clinical neurologist may see the ultrasound as an independent magnet.

00:02:23: In our laboratory we usually do ultrasonographic diagnostics after we realized that there is a loss of function in electrodiagnosis.

00:02:33: Ultrastound helps us then to identify the morphological correlates of this malfunction.

00:02:42: However, the reverse approach is also very valuable.

00:02:45: If a clinician using Ultrastound identifies pathological changes, he can thereafter let's check in electrodiagnosis if the changes result in functional impairment.

00:02:56: For this reason, I think neurophysiologists and also neurologists should be encouraged to learn the ultrasound of the nerves.

00:03:07: Ultrasound is cheap, can be used at bad site and does not have side effects.

00:03:11: Although it is inferior to other imaging modalities regarding its limited penetration, it is superior regarding spatial and time resolution and regarding its unique ability to perform dynamic imaging.

00:03:25: which means to visualize the nerves and other objects during passive or active movements.

00:03:31: Okay, so let's move to the technical side.

00:03:35: For someone new to this field, what kind of machine and transducer would you recommend?

00:03:41: What should they start with and why?

00:03:46: I think nowadays most of the equipment currently available in the clinics is good enough to rely on these kind of nerves.

00:03:54: If they were produced, Let's say, in the last ten years, most of them are suitable, they are good enough to scan the nerves.

00:04:04: Many has also a dedicated preset.

00:04:07: And if not, the other commonly preprogrammed presets, like musculoskeletal or small parts, are also suitable.

00:04:15: We usually use the linear transducer of twelve megahertz frequency and higher.

00:04:21: Some deeply located nerves, especially in obese patients, like for example the sciatic nerve may require a lower frequency and sometimes the curvilinear transducer.

00:04:32: Scanning in less accessible areas like for example axillary nerve in axillary fossa may require probes of specific shape like for example the hockey stick transducer.

00:04:45: What about the pitfalls?

00:04:47: What are the most common mistakes clinicians make when starting out?

00:04:52: The most common... mistake when starting out, but also later, is to mistake the other structure for the nerve and inversely.

00:05:03: For this reason, it is advisable at the beginning to practice scanning on yourself or on the colleague, optimally a slender one, and learn to identify firstly the normal, not pathologically changed nerves.

00:05:16: General remarks are that the nerve consists of hyper-echoic sheets, like perineurium.

00:05:22: and hypoechoic nerve fibers, which are surrounded by hyper-echoic clearly distinguishable epineurion.

00:05:32: All together resembling the honeycomb.

00:05:35: The nerve can also be distinguished from other structures by assessments of its anisotrophy.

00:05:41: In other words, by checking how much the nerve changes its eugenicity when scanning from different angles, it changes significantly less than independence, which are the structures most often mistaken for a nerve, but it changes more than the masses do.

00:05:59: And ultrasonographies should also be aware of artifacts, including acoustic shadowing and enhancement, which are the changes in the organicity of the object of interest, due to neighboring superficially located structure, which either reflects or almost all radiation, for example a bone, or reflects none or almost none of the radiation.

00:06:22: for example a ganglion.

00:06:24: Rarely in the ultrasound of nerves we can see also the reverberation artifact which results from the ultrasound wave reflecting back and forth from the highly eugenic surface and creating an image of evenly spaced lines.

00:06:40: We can see it especially when performing an ultrasound guided injections with the needle reverberating.

00:06:49: So technique and practice is everything.

00:06:53: Let's dive into the clinical scenarios, starting with the most common indication for nerve ultrasound entrapment neuropathies.

00:07:02: How does ultrasound improve diagnostic accuracy in something as common as carpal tunnel syndrome?

00:07:11: Ultrasound visualizes primary enlargement and hypoallergenicity of the median nerve and inlet to the tunnel.

00:07:19: It is usually best visible usually in between proximal and distal wrist crease.

00:07:26: It represents the reactive edema for the compression of the nerve which occurs in the tunnel.

00:07:35: The compression itself is somewhat difficult to visualize due to surrounding bones and other structures in the tunnel which cause shadowing.

00:07:44: It is also evident rather in advanced stages of the disease.

00:07:51: Beside the nerve enlargement at the tunnel inlet, there are also other sonographic signs of carpal tunnel syndrome, such as retiniculum bowing, nerve hypervascularization and others.

00:08:05: Ultrasound improves accuracy of the testing due to its high sensitivity.

00:08:10: In our laboratory, we see a lot of cases which are normal in nerve conduction studies, but show ultrasonographic signs of carpal tunnel syndrome.

00:08:20: Only rarer you will see the opposite.

00:08:23: Electrodiagnostic positive and ultrasound negative.

00:08:27: On the other hand, I have to say part of cases where enlargement of the nerve typical for carpal tunnel syndrome are accidental findings without clinical symptoms.

00:08:37: Maybe more important than the sensitivity is the ability of the ultrasound to visualize atypical changes in carpal tunnel syndrome or disorder which can mimic the carpal tunnel syndrome.

00:08:51: One of them is the presence of B-fit median nerve, which can be associated with normal or atypical nerve conduction findings.

00:09:00: The secondary carpal tunnel syndrome can occur due to compression of the nerve by the additional belly of a strong longus muscle or by the compression exerted by accessory abductor digitimini muscle.

00:09:17: The disorders which can mimic carpal tunnel syndrome is can be the presence of tenosynovitis or presence of ganglions and tumors within the tunnel.

00:09:28: A consensus has been recently established by the experts of the International Federation of Clinical Neurophysiology when the median nerve should be investigated with ultrasound.

00:09:39: It is when the symptoms suggest carpal tunnel syndrome, but nerve conduction is normal or atypical, when the clinician suspects that the nerve could be compressed by the element different than the flexor retinaculum, when the symptoms did not improve or are recurred after the decompression, and finally when the patient suffers also from generalized preneuropathy.

00:10:04: And what about unnerved neuropathy at the elbow?

00:10:08: As similar to carpal tunnel syndrome and also to other entrapment neuropathies, structural changes affecting the ulnar nerve may be visualized, which is not available with nerve conduction.

00:10:20: An example is the dynamic dislocation of the ulnar nerve during elbow flexion.

00:10:26: The nerve moves in that case to the medial side of the epicondylus and may be irritated or even damaged.

00:10:34: However frequent finding is the presence of the uncorneous epidrochlearis muscle which narrows the lumen of the cubital tunnel.

00:10:41: Less frequently, other pathological structures in the tunnel can be found, such as aneurysm or tumours.

00:10:49: Ultrasound can also document the presence of the nerve compression outside the cubitial fossa, but still close to the elbow joint.

00:10:57: Such compression may result from entrapment between the tendons of flexorocarpiularis muscle or compression by the third exostosis of the ulna, which may occur years after the fracture or eluxation of this bone.

00:11:12: These all findings help to decide if the neuropathy deserves surgical intervention which can be which can also be properly tailored.

00:11:23: Trauma is another area where ultrasound is incredibly useful.

00:11:27: How do we approach a suspected nerve raptor?

00:11:33: Yes, ultrasound is very important in this topic.

00:11:37: Ultrasound gives the opportunity to inspect the integrity of traumatized nerve.

00:11:44: For this reason, it's significantly improved the outcomes after NeuroTrauma.

00:11:48: Previously, like twenty years ago, management based only on nerve conduction status and needle electromyography.

00:11:58: That approach led often to wait even months with surgical intervention in the hope of spontaneous reinnovation occurring in repetitive electro-diagnostic tests.

00:12:08: Now, with ultrasound, it is possible to assess if the integrity of the nerve is preserved and if awaiting of spontaneous reinnovation is justified.

00:12:19: A high-class equipment allows sometimes inferring about the degree of traumatic neuropathy in the Sanderland classification, which Forther contributes to timely made decision about intervention.

00:12:32: Furthermore, ultrasound can identify hematomas, neuromas, compression or encasement of the nerve with, for example, bone debris, which may deserve surgical correction, even if the nerve community continuity is documented.

00:12:47: In general, ultrasound improved timing and accuracy of decision-making regarding the need of surgical intervention and its extension.

00:12:55: In some cases, also an intraoperative scanning using sterile gel may further help the surgeon and improve the outcome.

00:13:06: You've mentioned structural lesions and that naturally brings us to another important topic, nerve tumors.

00:13:14: What are the key red flags that clinicians should look for on ultrasound suggesting a tumor.

00:13:21: What makes you think this is something more than just an entrapment?

00:13:28: In general, the ultrasonographist should suspect there is a tumor when he sees an abnormal mass with continuity with one of the nerves, parrots or pexels.

00:13:44: The shape of tumor, neural tumor, may vary.

00:13:48: from nearly spherical neuromas and schwannomas, the fusiform neurofibromas, or more irregular magnet processes.

00:13:56: Withersonal graphic inspection by suspicion of the tumor should include also color doppler or other modality to investigate the vascularization and if possible also the velocity of the intratumoral blood flow.

00:14:13: In general, a rich, chaotic vascularization with fast high-resistant flow indicates malignancy.

00:14:21: A fast growth of the tumor in the control investigation speaks for malignancy as well.

00:14:27: The third part of inspection is the application of pressure with transducer upon the tumor with assessments of its deformation ability and of pain, which is triggered by giving pressure.

00:14:41: The pain may be local or may radiate along the nerve, This may be also called a sonographic thinness sign.

00:14:51: Tumors of peripheral nerves are rare and therefore may be overlooked.

00:14:55: Clinically, they could be mistaken for enlarged lymph nodes.

00:15:00: In our laboratory, we find them most often after obtaining an atypical electrodiagnostic results.

00:15:08: Most of them will be benign like neuromas, schwannomas, neurofibromas, or fibrolipomas of the nerve.

00:15:16: Malignant ones are sarcomas originating from the neural sheets or connective tissue of or myelin.

00:15:22: A high class equipment may allow to infer about the type of the tumor to some degree.

00:15:28: However, the biopsy is always indicated.

00:15:33: So when should neurologists consider a surgical consult?

00:15:40: Okay, surgeon will be always needed to perform the biopsy.

00:15:44: And this biopsy may be done along with entire tumor resection or not.

00:15:50: His pathological assessments should always be made.

00:15:53: In further management, clinician may take his own decision not to manage the tumor operatively.

00:16:00: This may be justified in benign, not significantly growing on our asymptomatic processes.

00:16:06: Regular sonographic control is, however, always indicated.

00:16:11: Let's talk about inflammatory neuropathies.

00:16:15: What does CIDP look like on ultrasound?

00:16:21: C-IDP is characterized by enlargement and hypogenicity of structures of peripheral nervous system, reflecting the inflammatory edema.

00:16:32: In this, it is similar to other inflammatory and some inherited neuropathies like Guillain-Barre syndrome, multifocal motor neuropathy, or Charcot-Marie II-Ia, PEP Ia.

00:16:47: Yet the topography distribution of these changes differs.

00:16:51: In CIDP, mostly the proximal segments of nerves, along with plexus and roots, are affected.

00:16:58: It is worth mentioning that sonographic changes doesn't need to be visible on the same locations as the neurophysiologic findings typical for CIDP, which are conduction slowing, conduction block or dispersion of the neurophysiologic responses.

00:17:16: Other inflammatory neuropathies can be characterized by less prominent changes like Guillain-Barre syndrome, or the changes may be more focal, like in multi-focal motor neuropathy or vasculitic neuropathy.

00:17:30: On the other hand, in Charcot-Marie II, nerve enlargement and hypoallergenicity will affect entire peripheral pathways, usually in a very symmetric way.

00:17:42: It will reflect rather not the inflammatory limb, but the but the pathologic hypertrophy of the nerves.

00:17:54: And from your own practice, do you have a memorable case where ultrasound changed the diagnosis?

00:18:03: I have many.

00:18:05: Maybe I can tell about a lady, forty years old, who came to our laboratory to have a test towards carpal tunnel syndrome.

00:18:15: She had typical symptoms with numbness, exacerbation during night, and with objects.

00:18:20: falling out of her hand.

00:18:22: She had no comorbidities.

00:18:25: Electrodiagnostic finding was atypical with motor conduction slowing on the forearm and with normal sensory conduction of the median nerve.

00:18:35: Ultrasound showed fusiform tumor which then after biopsy turned out to be a neurofibroma.

00:18:42: Further similar tumors were seen along the median nerve also in the arm and then also on her ulnar nerve on the same side.

00:18:51: We expanded the investigation and we counted than eleven tumors on her nerves of upper extremities and also on one tumor on her nerves of the lower extremities, the left tibial nerve.

00:19:04: All the tumors except the one most distilled on her left medial nerve were asymptomatic.

00:19:11: The genetic diagnostic towards neurofibromatosis one and neurofibromatosis two was negative.

00:19:17: The patient still awaits the results from the tests towards more uncommon causes of multiple neurofibromas.

00:19:27: When it comes to nerve lesions, do you find any other useful applications for ultrasound?

00:19:35: What we're mentioning is the neurologic amyotrophy, also called the Personage-Tunnel Syndrome, where ultrasound reveals occasionally nerve constriction with nerve torsion, which requires surgical intervention the surgical nerve detortion.

00:19:52: Some neurologists and also anesthetics use also the ultrasound to do peri-neural injections, which bring relief to pa- of pain, especially in entrapment neuropathies.

00:20:05: The most popular one, which we also do occasionally in our lab, is the hydrodecompression of medium nerve in the carpal tunnel syndrome.

00:20:14: It may resolve the symptoms for up to one year period.

00:20:17: During this intervention, One has to direct the stream of injection so that it dissects the nerve from the flexor retinaculum.

00:20:27: You can use injection with steroids or mixed with lignocaine, although the use of dextrose is also practiced.

00:20:36: Afroentrapment syndromes can be also managed with such ultrasound-controlled injections.

00:20:41: In our lab, we occasionally inject also lignocaine around the lateral cutaneous femoris nerve in patients with parasitic meridia.

00:20:50: and results are really excellent and durable.

00:20:55: That's really interesting.

00:20:56: It shows how versatile ultrasound is and it's worth learning this tool and getting it no better.

00:21:05: So before we close, what are your top practical tips from experts for clinicians learning their ultrasound?

00:21:14: It is always advisable to have a good textbooks and a mentor.

00:21:18: However, in ultrasound, the most important thing is the practice.

00:21:22: You should practice on the colleagues and also on patients if it is not bothering them too much.

00:21:28: Initially, you don't need to make decisions on your first findings, especially if you don't have someone to ask or to repeat your scanning.

00:21:36: But you should practice.

00:21:38: It is the only way to teach your eye and your hand how to discern the nerve from other tissues, how to follow the nerve, or how to switch from the cross-sectional to longitudinal nerve presentation.

00:21:49: At the beginning, make sure that the ultrasound is something you really like and that your findings bring you joy and satisfaction.

00:21:57: Thank

00:21:57: you so much for joining us and sharing your expertise.

00:22:03: Thank you for having me again.

00:22:07: And thank you to our listeners.

00:22:09: If you enjoyed today's episode, stay tuned for upcoming topics on the EANcast.

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