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Abstract
Myofibrillar myopathies (MFMs) are a group of rare genetic disorders that affect the function of skeletal, cardiac and smooth muscle.
MFM exhibits a considerable degree of clinical heterogeneity. In numerous instances of MFM, muscle weakness is the predominant manifestation. Certain MFM subtypes are distinguished by respiratory and cardiac impairment.
There is little information available about anaesthetic management in MFM, and even less is known about obstetric anaesthesia.
A successful case of a patient with MFM undergoing a caesarean section under combined neuraxial anaesthesia is reported. The patient experienced no complications, and functional recovery was swift.
- Anaesthesia
- Obstetrics, gynaecology and fertility
- Musculoskeletal and joint disorders
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Background
Myofibrillar myopathies (MFMs) are a group of rare, hereditary muscle diseases that affect the myofibrils. They are a relatively new group of chronic myopathies characterised by destruction of the muscle fibre at the Z-disk, accumulation of degradation products and consequently loss of structure and function of skeletal, cardiac and smooth muscle.1
At least eight different proteins have been identified as genetic causes, all related to proteins in the Z-disk.1
MFM is a condition with significant clinical variability, which can mimic the symptoms of other myopathies such as distal myopathy, limb-girdle muscular dystrophy, among other patterns. Muscle weakness is the primary symptom in many cases of MFM, although not all patients present with this symptom.2
Weakness typically starts in the lower extremities and can spread to the upper body, although there may be other patterns of progression as well. Some subtypes of MFM are characterised by cardiac and respiratory involvement.
Most patients experience gradual onset of muscle weakness in middle age, which can progress to severe disability and premature death. MFM is difficult to diagnose due to its variability, and muscle biopsy is currently the most definitive diagnostic tool.2 There are currently no effective therapies to slow the progression of the disease.2 Serum creatine kinase (CK) levels can vary depending on the subtype and individual patient.3
There is currently limited information available on the specific effects of MFM on mode of delivery. Caesarean delivery may be indicated in MFM, depending on the specific subtype and severity of the disease. In some cases, there may be a higher risk of complications during vaginal delivery due to muscle weakness and respiratory or cardiac involvement.
While there is some limited knowledge about the management of anaesthesia in patients with MFM,4 there is even less information about its specific management during obstetric procedures. Due to the potential risks associated with anaesthesia in patients with neuromuscular disorders, it is essential to have a multidisciplinary team involved in the decision-making process regarding obstetric procedures, including caesarean delivery, in patients with MFM.
We present successful management of a patient with myofibrillar myopathy undergoing a caesarean section under combined neuraxial anaesthesia.
Case presentation
We present a case of Caucasian woman in her 40s evaluated in the anaesthesiology consultation. She was 34 weeks pregnant following in vitro fertilisation and was scheduled for an elective caesarean section. The pregnancy had been followed up in a high-risk consultation pathway and had been uneventful.
The patient was classified as American Society of Anesthesiologists (ASA) III due to a diagnosis of myofibrillar myopathy in 2014, caused by a DES/desmin mutation. This mutation is often associated with cardiac and respiratory involvement, and according to national records, this is the only reported familiar case in Portugal.
She was regularly followed up in neurology and was not taking any regular medication. In terms of clinical presentation, she displayed a gait with a pelvic tilt and steppage, along with both proximal and distal amyotrophy in her lower limbs, specifically affecting her pelvic girdle and peroneal muscles. The patient did not exhibit any bulbar or respiratory compromise, therefore, no respiratory function tests were performed. There was no worsening of her condition during the pregnancy. However, the patient reported feeling fatigued during the last trimester.
She had a history of four general anaesthetics for in vitro fertilisation, with no complications, namely malignant hyperthermia (MH) or rhabdomyolysis. On physical examination, she had no signs of a difficult airway, Mallampati score 1 and normal cardiopulmonary auscultation. Anthropometric data included weight of 57 kg and height of 1.60 m, both measured on the day of the consultation.
The blood tests showed normal complete blood count and biochemistry, with normal CK levels. Despite normal previous tests, a new ECG and echocardiogram were requested at the end of the pregnancy, which were also normal.
After evaluating the patient and her clinical condition, the planned anaesthetic technique was combined spinal–epidural anaesthesia, with monitoring following the standard ASA guidelines and waveform capnometry via nasal cannula.
The procedure was performed in a sitting position, with the epidural space located at L3/L4. Hyperbaric bupivacaine 0.5% 7.5 mg and sufentanil 2.5 µg were administered intrathecally. The epidural catheter was advanced 4 cm into the epidural space and secured. The technique was performed without complications.
An appropriate sensory block was achieved (T5/T6), and the patient had an uneventful caesarean section. Haemodynamic stability without the need for vasopressors and spontaneous ventilation were maintained, with adequate respiratory dynamics. Body temperature was monitored and preserved within normal range. Adequate fluid therapy was maintained during the intraoperative period. She was observed in the recovery room until the discharge criteria were met, with cardiopulmonary stability. Motor and sensitive blockade reverted within the expected timeframe. She maintained the epidural catheter for postoperative analgesia with epidural morphine for 24 hours, according to the hospital protocol.
Outcome and follow-up
The patient was evaluated by the anaesthesiologist on the first day after the caesarean section, who conducted a brief neurological examination. She had normal vital signs, had begun to mobilise and was able to care for the new-born.
She was assessed during her hospitalisation by the neurologist who was following her, conducting a thorough neurological examination. The neurological examination excluded any new deficits or worsening of the previous muscle pattern. There was no decompensation of the cardiorespiratory condition.
The blood tests remained within normal limits, with no increase in CK levels. The patient was discharged from the hospital on the second day after the caesarean section. Additionally, she was referred to neurology consultation for further monitoring and evaluation of her chronic condition.
Discussion
MFM is a rare and heterogeneous disorder; however, there are multiple aspects that need to be considered, given its profound impact on the skeletal, respiratory and cardiac systems.
Little is known about this condition and there is only one report in the literature regarding the anaesthetic management of a patient with MFM.4
Managing anaesthesia for patients with myopathies can be difficult. These disorders are rare and have a wide range of symptoms and associated conditions. Appropriate preoperative evaluation is essential to optimise anaesthetic management and reduce the risk of perioperative complications.
The case of our patient was diagnosed and documented, and there is a high probability that families affected by myopathies will test their children early and have a precise diagnosis at the preoperative anaesthesia assessment.
However, there is still a risk of undiagnosed myopathic patients undergoing routine operations, particularly patients with subclinical or late-onset symptoms. Knowing the key clinical symptoms is crucial for identifying potentially undiagnosed patients who require further investigations. In cases of suspected diagnosis, if genetic testing is available, it should be performed.
The questions surrounding the risk of MH, rhabdomyolysis, sensitivity to anaesthetic agents and neuromuscular blockade can be particularly perplexing with any neuromuscular disorder.4 In the reported case, no complications were recorded, similar to what was described in the first literature report.4
The risk of MH in different hereditary disorders is not well-defined in the literature, including MFM.5 MH is a rare occurrence, and some genetic mutations have been identified as risk factors. MFM is not associated with these previously described mutations.6 Some ultrastructural features may overlap between MFM and myopathies that carry a risk for MH, such as central core disease. However, there are other ultrastructural findings that are unique to MFM and distinguish it from these disorders.7
There are currently no reported cases of MH in patients with desminopathy or other subtypes of MFM. Therefore, while it is not possible to definitively state that the risk of MH is zero, there is currently no evidence to suggest a potential mechanism for MH susceptibility in these patients.
Although our patient had undergone previous general anaesthesia without any recorded complications, it is important to note that the absence of adverse events in previous anaesthetic exposures does not exclude the possibility of a predisposition to MH or anaesthesia-induced rhabdomyolysis (AIR).
AIR is a condition in which muscle breakdown and release of intracellular contents occur due to anaesthesia, leading to an increase in serum CK levels. This condition can be mistaken for MH. Succinylcholine and possibly inhaled anaesthetics have been linked to AIR, particularly in patients with elevated CK levels.
As general anaesthesia poses an inherent risk for severe complications in myopathic patients, regional anaesthesia techniques may be a safer option for patients with MFM and should be prioritised whenever possible. Additionally, these techniques have been proven to have benefits in obstetric anaesthesia. Regional anaesthesia enabled the avoidance of other drugs that require special attention in patients with myopathies, such as non-depolarising muscle relaxants.
Another advantage is related to the airway management and the risk of aspiration. Myopathies can also affect smooth muscle cells and the gastrointestinal tract, leading to an increase the risk of aspiration. Although our patient did not present with bulbar symptoms, pregnancy itself is associated with reduced lower oesophageal sphincter pressure and increased risk of reflux regurgitation and aspiration.
In terms of intraoperative monitoring, in addition to the standard, the use of waveform capnometry in patients with MH linked myopathies can serve as an early indicator of hypermetabolic states. Although there is no direct connection between MFM and MH and despite the regional technique used, we monitored this parameter due to the additional information it provides, as it is a non-invasive and cost-effective technique.
Intensified cardiovascular surveillance techniques should be implemented with a low threshold. For patients with cardiomyopathy, invasive blood-pressure monitoring is recommended. Additionally, immediate access to blood gas samples ensures early detection of postoperative pulmonary dysfunction. In view of the patient’s stable cardiopulmonary condition, invasive monitoring was deemed unnecessary. Tight temperature management and prevention of hypothermia are strongly indicated in all myopathic patients. Avoiding hypothermia and shivering is important as it can induce severe myotonic reactions or paradoxical paralysis. Maintenance of normothermia was a concern in the case presented.
Due to the high prevalence of comorbidities, myopathic patients are a high-risk population that frequently necessitates intensive postoperative monitoring. In addition to potential cardiopulmonary complications, episodes of MH and AIR may occur during the postoperative period. Regional anaesthesia may play a role in reducing postoperative complications.
In addition to the management of the immediate perioperative period, this group of patients may require ongoing multidisciplinary care and rehabilitation to optimise their long-term outcomes. Our patient presented cardiopulmonary stability in the postoperative period, with complete functional recovery, able to ambulate and provide care to the new-born on the first day.
Learning points
Myofibrillar myopathy (MFM) is a rare condition with profound effects on the skeletal, respiratory and cardiac systems. There is limited knowledge about the anaesthetic approach in this disease, with only one reported case in the literature. Even less is known about obstetric anaesthesia.
Managing anaesthesia in patients with myopathies can be challenging, and appropriate preoperative evaluation, with special attention to cardiopulmonary function, is essential to optimise anaesthesia management and reduce the risk of perioperative complications.
Regional anaesthesia techniques may be a safer option for patients with MFM and should be prioritised whenever possible.
The uncertainties related to the potential for malignant hyperthermia, rhabdomyolysis, heightened sensitivity to anaesthetic agents and susceptibility to neuromuscular blockade can be particularly challenging when dealing with any type of neuromuscular disorder.
Ethics statements
Patient consent for publication
Footnotes
Contributors The following authors were responsible for drafting of the text, investigation and critical revision for important intellectual content; gave final approval of the manuscript: DCLF, ACFF, SZ and SCCF
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.