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September 14, 2022 | by Catrina Hacker, PennNeuroKnow

Whether it’s walking to the grocery store or hugging a friend, movement is a central part of how we interact with the world. We don’t usually think about how we’re able to move, but every motion is part of a beautifully efficient process that coordinates a complicated network of cells across the nervous system. When neurological disorders disrupt this coordination, the efficiency of our motor system breaks down, which can lead to a variety of movement disorders and produce a broad range of symptoms. Movement disorders are a common symptom across the many types of autoimmune encephalitis (AE) and can be especially important to the diagnosis of AE in children.

Learning the language of movement disorders

The scientific literature is littered with dozens of specialized terms doctors use to describe movement-related disorders. For doctors, these terms are helpful because they can precisely describe specific symptoms that help them distinguish between different diagnoses, but they can be intimidating to non-medical readers. To begin, let’s break down a few important terms describing the disorders most common in various types of AE. Please note that this is not an exhaustive list and is only meant to capture some of the most common movement disorders that can result from common types of AE. (Click the name of the disorder to watch a Youtube video demonstrating some of these symptoms.)

Ataxia. Ataxia describes difficulty balancing and coordinating movements. In the most classic presentation of ataxia patients struggle with walking and running, particularly in situations that require more coordination such as walking up and down stairs1. Patients with ataxia can have a high risk of falling and in some cases they might have difficulty coordinating the movements necessary for speaking or writing2. One type of ataxia is thought to be caused by degeneration of neurons in a brain region known to be important for movement called the cerebellum1,2.

Chorea. Patients with chorea make involuntary, random movements. These brief and random movements are not repetitive or rhythmic but do appear to flow from one muscle to the next3. Chorea can occur in any muscle group, ranging from fingers and toes to facial movements. Interestingly, chorea subsides when patients are asleep4. Chorea is associated with too much activity of a neurotransmitter called dopamine that plays an important role in coordinating and initiating movement3,4.

Dystonia. Patients with dystonia experience involuntary muscle contractions that result in abnormal postures and repetitive movements. These contractions can occur anywhere on the body and are often painful. Like ataxia, dystonia can cause problems with speech and handwriting. In addition, patients with dystonia might experience foot cramps or drag their foot after prolonged exercise5.

Myoclonus. Myoclonus is a broad term describing sudden, involuntary jerking of muscles. This often involves twitching of a muscle followed by relaxation. If you’ve ever jerked awake while drifting off to sleep you’ve experienced a benign myoclonic jerk (this is not worrisome as an isolated event). Myoclonic jerks can occur on their own or be associated with different disorders6. The movements in myoclonus are quick and simple, while the movements in chorea tend to be slower and continuous. (Hear directly from a patient about her experience with dystonia and myoclonus here)

Movement disorders across different types of autoimmune encephalitis

While many types of AE can result in movement disorders, some subtypes have unique symptoms that distinguish them from others. Sometimes movement disorders are one of the most prominent symptoms to present themselves, whereas in other cases they may be more subtle and secondary to other psychiatric symptoms. Here we will discuss some of the subtypes of AE that most commonly result in movement disorders.

Several movement disorders often present together in patients with anti-NMDAR AE, the most common AE. Chorea and dystonia are observed in up to 90% of Anti-NMDAR patients7. While they can affect all limbs, in anti-NMDAR encephalitis they most characteristically affect the face and mouth8. In some cases these might be the first signs of the disease, so a clinician should consider the possibility of AE when patients visit the clinic with complaints of movement-related symptoms7.

Movement disorders are some of the most common symptoms of CASPR2-antibody associated encephalitis. Ataxia is observed in up to a third of patients and can be the only presenting symptom at disease onset, with other symptoms developing later7. The ataxia in CASPR2-encephalitis patients often manifests as a strong gait disturbance8 that occurs in brief, but frequent, bursts7. CASPR2-encephalitis can also present with a distinct form of myoclonus that distinguishes it from other kinds of AE. This form of AE is most common in elderly men9, and myoclonus of the lower limbs is often observed when patients are walking or standing. Spinal myoclonus leading to spasms around the abdomen has also been observed in CASPR2-encephalitis patients7. Finally, in some cases chorea is a prominent movement-related symptom of CASPR2-encephalitis7.

IGLON5-antibody associated encephalitis can also present with many movement disorders. While the best indicator of IGLON5-encephalitis is sleep disorders, some patients have also been reported to have chorea7. Another movement disorder reported in some IGLON5-encephalitis patients is axial rigidity, or rigidity in the trunk and hips. These movement disorders can make it difficult for patients with IGLON5-encephalitis to walk and balance and can put them at risk of falling8.

Many other types of AE are associated with movement disorders including (but not limited to) GlyR-, DDPX-, LGI1-, and mGluR1-antibody associated encephalitis7,8. It is important to note that although movement disruptions are common in many types of AE, they are rarely the only symptom and are not diagnostic on their own7,8,10. Instead, they can serve as one of many clues leading doctors toward a correct diagnosis. The neural explanation for how each type of AE leads to these movement disorders is not well understood. Determining the biological basis of the relationship between AE and movement disorders is an important area for future research that might help us to better understand these distinct subtypes of AE.

Movement disorders in children and adults with autoimmune encephalitis

In addition to distinguishing different types of AE, movement disorders are proving to be an especially important diagnostic tool for children with AE. Movement disorders can be observed in both children and adults, but they are more common in children, particularly those with anti-NMDAR AE. The presentation of anti-NMDAR AE in adults is now well understood and typically involves psychiatric symptoms and cognitive impairment as well as the movement disorders described above. The presentation of anti-NMDAR AE in children isn’t as well documented, but diverges from adults in that it more often includes seizures and movement disturbances7,10,11.

In many cases, movement disturbances are the first or only presenting symptom in children with anti-NMDAR AE. One set of case studies showed that four young patients eventually diagnosed with anti-NMDAR AE all initially presented with difficulties walking or coordinating movement10. Another study considered 50 cases of children with anti-NMDAR AE and found that motor deficits including dystonia of the hands and feet are key in diagnosing focal seizures that often accompany AE in these patients11. The initial presentation of anti-NMDAR AE can be ambiguous, and treatment is often delayed because a diagnosis is not immediately made. The presence of movement disorders and other disturbances (e.g., those accompanying seizures) along with other symptoms could be key signs to consider a diagnosis of AE in children10.

The diversity of movement disorders in various types of AE mirrors the diversity of the diseases themselves. Whether in distinguishing subtypes of AE or diagnosing children, they are a powerful spotlight under which the diversity of AE can be interrogated. Despite our growing understanding of how movement disorders can be used to diagnose various types of AE, there is still very little understanding of why different types of AE cause different types of movement disorders. Future work can leverage these known differences in movement disorders associated with different types of AE to better understand their biological basis and hopefully develop better treatments and cures. 

References

  1. Ataxias and Cerebellar or Spinocerebellar Degeneration | National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/disorders/ataxias-and-cerebellar-or-spinocerebellar-degeneration.
  2. Kuo, S.-H. Ataxia: Contin. Lifelong Learn. Neurol. 25, 1036–1054 (2019).
  3. Chorea | National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/disorders/chorea.
  4. Bhidayasiri, R. Chorea and related disorders. Postgrad. Med. J. 80, 527–534 (2004).
  5. Dystonia | National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/disorders/dystonia.
  6. Myoclonus | National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/health-information/disorders/myoclonus.
  7. Gövert, F. et al. Antibody-related movement disorders – a comprehensive review of phenotype-autoantibody correlations and a guide to testing. Neurol. Res. Pract. 2, 6 (2020).
  8. Uy, C. E., Binks, S. & Irani, S. R. Autoimmune encephalitis: clinical spectrum and management. Pract. Neurol. 21, 412–423 (2021).
  9. van Sonderen, A. et al. The clinical spectrum of Caspr2 antibody–associated disease. Neurology 87, 521–528 (2016).
  10. Yeshokumar, A. K., Sun, L. R., Klein, J. L., Baranano, K. W. & Pardo, C. A. Gait Disturbance as the Presenting Symptom in Young Children With Anti-NMDA Receptor Encephalitis. Pediatrics 138, e20160901 (2016).
  11. Favier, M. et al. Initial clinical presentation of young children with N-methyl- d -aspartate receptor encephalitis. Eur. J. Paediatr. Neurol. 22, 404–411 (2018).

 

 

 

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