Acute Motor Axonal Neuropathy (AMAN), a Variant of Guillain-Barre Syndrome: A Case Study

Abstract

This case study documents a fictional description of a patient presenting with acute motor axonal neuropathy (AMAN), which is an axonal classification of Guillain-Barre Syndrome . The patient’s experience in acute care is discussed briefly, while the patients’ sub-acute and long-term rehabilitation is covered in more detail. The purpose of this case study is to highlight approaches to assessment, outcome planning, and treatment interventions in the context of a community-based rehabilitation setting during the sub-acute phase of the disease. The case study is unique as it employs an interdisciplinary approach and international classification of function, disability, and health (ICF) framework to address the pathology of the disease in a patient-specific manner.

Introduction

Acute motor axonal neuropathy (AMAN) is a variant type of Guillain-Barre Syndrome (GBS). AMAN is a non-inflammatory disease whereby axons of motor nerve cells are selectively targeted and destroyed by the body’s own immune system. The myelin sheath surrounding the axon is unaffected. Studies suggest that the body’s immune system specifically attacks the membrane surrounding the axon called the axolemma. AMAN is characterized by acute progressive motor weakness, areflexia, ataxia, oculomotor dysfunction and absence of sensory symptoms. AMAN is typically preceded by an infection from bacteria called Campylobacter jejuni or Haemophilus influenzae. Prevalence of AMAN is estimated at 5% of cases in North America and Europe, while 30-65% of cases are located in Asia, Central and South America.

While the prognosis involves two categories of patients undergoing rapid recovery or slower recovery after reaching the highest levels of unchanging symptoms and dysfunction, or plateau phase. It is proposed that recovery is achieved through mechanisms such as terminal motor nerve axonal regeneration and collateral re-innervation processes. Patients with AMAN continue to see improvements in ambulation up to four years post-diagnosis.

This brings us to the purpose of the following case study of a patient with AMAN. Physiotherapy assessment and treatment can help prevent the decline of functional status and maintain functional independence, muscle strength, posture, balance, and cardio-respiratory fitness. Moreover, it enables an individual to continue performing self-care routines and activities of daily living (ADLs). In accordance to the International Classification of Functioning, Disability and Health (ICF) framework, the primary objective of this case study is to elaborate on how physical therapy rehabilitation assessment and treatment interventions can aim to address body structure and function impairments, activity limitations, and participation restrictions in patients with AMAN. The case study further aims to focus on patient-centred care and an interdisciplinary approach to assessment and management of AMAN in a community-based rehabilitation setting.

Case Background

Trish Jones, 62 year old female, initially presented with nausea and diarrhea one week after returning home from vacation in Mexico. Due to COVID-19 travel restrictions, Trish refrained from visiting the hospital’s emergency department. Instead, Trish booked an appointment with her family doctor in two weeks’ time after her quarantine was finished. Over the next week, Trish complained of progressive muscle weakness in her hands and feet. She had difficulty grasping items with her hands and reported difficulty with climbing stairs. During the subsequent week, Trish reported decreased coordination while ambulating and unusual shortness of breath and fatigue. Prior to the visit with her family doctor, Trish lost her balance and fell while walking upstairs, which led to admission to the hospital’s emergency department.

After diagnostic investigation, Trish was diagnosed with acute motor axon neuropathy caused by Campylobacter jejuni, and was treated immediately with a high dose of intravenous immunoglobulin (IVIg) therapy. Trish spent the next two weeks in the intensive care unit (ICU), where she required mechanical ventilation due to respiratory muscle weakness. The acute health care team performed passive range of motion, splinting, airway clearance techniques, and frequent repositioning to prevent the development of contractures, deep vein thrombosis, pressure ulcers, and other complications. Prior to discharge, Trish was educated about and fitted for a 4-wheel rollator to assist in her recovery. It has been 12 weeks since she was discharged from the hospital. No other medical conditions or comorbidities have developed, and her medical status has remained stable.

The sub-acute phase of rehabilitation will be patient-specific, utilizing an ICF framework to address body function and structural impairments, activity limitations, and participation restrictions. In addition, health care providers will employ a safety-based approach to prevent patient exhaustion, and promote patient confidence in performing functional activities or tasks.

Patient Profile

Patient Profile (PP): Trish Jones, 62 year old female

Medical Diagnosis: Acute motor axonal neuropathy

Nature of the Condition: Sub-acute phase of the disease, in recovery

Primary Complaint:

• Weakness in muscles of hands, wrist, ankle, and feet,
• Fear of falling
• Decreased mobility and coordination
• Self-reported fatigue

Past Medical History (PMHx)

• Rotator Cuff Surgery 10 years ago (fully healed and no associated functional impairments)
• Campylobacter jejuni infection 12 weeks ago

Medications (Meds): High dose of intravenous immunoglobulin (IVIg) therapy as needed

Primary Reason For Referral: Recovery from AMAN

• Inability to perform certain ADLs without assistance
• Mobility levels, balance, coordination, joint range of motion, muscle strength/endurance have not returned to pre-AMAN levels
• Decreased aerobic capacity contributing to feelings of fatigue
• Decreased participation in previously enjoyed leisure activities/hobbies and physical activities

Intervention

The purpose of the interventions listed are to:

• Help patients to maintain and regain muscle strength, ROM, and function during the remyelination process. It is important to note that although therapy does not directly facilitate nerve tissue repair, it allows patients to optimally use the muscles during the healing process.
• Creating a patient-centered treatment plan following the ICF framework to address body function and structure impairments, activity limitations, and participation restriction
• Educate patients on the proper use of mobility aids and functional adaptations that allow patients to resume activities as close to their previous level of activity.
• Will use a safety-based approach to help patients recognize and perform activities in ways they feel safe to do so.

Management program during recovery phase

General notes for exercises:

• Exercises should be matched to patients activity, performed in short intervals and not overly fatiguing.
• Exercise progression should only occur when patient shows improvement in exercises for a week, without deterioration of status (ie. increased fatigue)

Intervention	Rationale	FITT (frequency, intensity, time, type) principles	Additional Notes
Education: Proper postural education (neutral spine, sitting up tall, shoulders back) and management (recommend postural adjustments that will help her maintain proper posture - lumbar roll) Safety consideration when using a gait aid Understand disease progression, prognosis, patient-specific goals, and treatment plan Role of caregiver (supportive and motivating but should encourage patient self-managment) Indicators to decrease or increase the level of intervention, and safety associated with each exercise	Having the patient understand the development and progress of their condition can increase patient buy-in, increases patient safety, and allows patients to take a larger role in their own rehabilitation.	Education should begin during the first session of therapy. Use of pamphlets or videos may be helpful too.	As therapists, it is important to encourage patients without making promises on patient’s recovery time and degree of recovery
Range-of-motion: Neuro-proprioception techniques to facilitate ankle dorsiflexion and plantarflexion	AAROM and PROM techniques that facilitate ankle ROM, to keep existing neuro-muscular junctions active, to encourage motor control.	10 reps x 3 times/day, performed daily Even if muscles are weak and full ROM cannot be achieved independently, the patient is encouraged to visualize the action during the exercise	Since sensation is not lost in these patients, can use external cues on on leg to promote muscle contraction PROM can be assisted by the therapist AAROM can be done as part of the home intervention plan using a belt to assist with ankle dorsiflexion PROM technique can be done in rehabilitation or by a caregiver in a home setting.
Muscle strengthening: Examples include: supine glute bridges seated hip flexion mini-squats with hands supported on counter/ stable surface theraband-resisted shoulder flexion and abduction bicep curls	Continue to strengthen and maintain larger lower (ie. quadriceps glutes, and hamstring) and upper extremities (ie. biceps and tricep) and trunk prime movers, as these are required to regain previous activity levels and function	8 reps x 3 sets with adequate rest in between (patient dependent) 3x/wk Intensity: low to moderate level of exertion Type: isometric and isotonic resistance training	Patient should be aware of fatigue levels using the Rate of Perceived Exertion on the Borg Scale (begin at low intensity and progress to moderate intensity) Multi-joint exercises can also be included as it encourages muscle synergies (coordinate prime mover and stabilizer action) Should be taught in rehabilitation and performed in home setting.
Grip Strengthening: Hand therapy GRASP (graded repetitive arm supplementary program)	This program focuses on upper extremity strengthening, fine motor tasks and repetitive functional tasks. Although this program is only validated in the acute stroke population, this can be beneficial if adapted to patients ability to improve grip strength and general upper functional outcomes.	1 hour of exercises, daily 8 weeks Remember to modify and adapt exercise to patient-specific fatigue levels, allow for rest as necessary	GRASP is a “homework-based” program that can be performed at home. Should be done in home setting.
Cardiovascular aerobic training: Examples Walking using gait aid Arm Cycle ergometer Stationary bike	Safe, low-level, aerobic exercise that does not go past level of fatigue is indicated for positive clinical outcomes	30 min total (can be broken up into 5-10 minute bouts) 3x/week Recommended to do walking with 4-wheeled rollator as this is a most functional activity	Patient should be aware of fatigue levels using the Rate of Perceived Exertion on the Borg Scale (begin at low intensity and progress to moderate intensity) Can be done in rehabilitation or home setting.
Balance and Gait Parallel bar gait training (walking, weight shift, challenge balance) Body weight treadmill Educate proper and safe use of gait aid	Training balance can help improve patient’s confidence in functional activities that require balance and help patients improve motor control patterns	Always perform this in a safe setting and with a therapist spotting the patient. Can be performed in a home setting if caregiver is taught the proper way to support patient. Use of ankle-foot orthosis as indicated Use gait belt for safety as indicated	By using a body weight treadmill, the patient may feel safer and more comfortable to ambulate without holding on to a support as they are supported by a harness. External facilitation to encourage ankle dorsiflexion and plantarflexion as indicated. Parallel bar and body-weight treadmill can be done in rehabilitation setting.
Functional Training Step up Sit to stand Reaching for objects while standing Adapted pilates (e.g seated pilates)	Putting it all together: Functional training takes a multifaceted approach to help patients strengthen, improve ROM, coordination and balance in a patient relevant	10 reps (or as many as tolerated), 2x/day preformed daily For pilates perform 1-2x/wk When these exercises are performed at home, make sure that they are performed safely and within the patient’s limit to prevent excessive fatigue	Patient should be aware of fatigue levels using the Rate of Perceived Exertion on the Borg Scale (begin at low intensity and progress to moderate intensity) Can be done in rehabilitation or home setting.