Median Arcuate Ligament Syndrome: Symptoms, Types, Causes and Treatment

Median Arcuate Ligament Syndrome (MALS), also referred to as celiac artery compression syndrome or Dunbar syndrome, is a rare but increasingly recognized vascular condition. It results from the compression of the celiac artery and surrounding nerves by the median arcuate ligament, a fibrous band of the diaphragm. This syndrome is notorious for its vague, overlapping symptoms, challenging diagnosis, and individualized treatment approaches. Understanding MALS requires a deep dive into its clinical presentation, subtypes, underlying causes, and the evolving landscape of treatment options. In this article, we break down each of these aspects to provide a comprehensive, human-focused overview of MALS.

Symptoms of Median Arcuate Ligament Syndrome

MALS is often described as a diagnostic puzzle, largely due to the non-specific and variable nature of its symptoms. Most patients experience chronic, recurring abdominal discomfort, but the precise characteristics and severity can differ widely. Recognizing the symptom patterns is crucial for early suspicion and diagnosis.

Symptom	Description	Frequency/Context	Source(s)
Epigastric Pain	Pain in the upper abdomen, often postprandial or with exertion	Most common, often severe	1,2,3,4,5,7
Nausea/Vomiting	Sensation of queasiness or actual vomiting episodes	Common, especially after meals	1,2,4,5
Weight Loss	Unintentional, often significant	Associated with chronic symptoms	1,2,3,4,5
Exercise-Induced Pain	Pain during physical activity	Less common, but notable	2,3
Anorexia	Loss of appetite	Occasional	5
Delayed Gastric Emptying	Bloating, fullness, slow digestion	In some cases with associated disorders	6

Table 1: Key Symptoms

The Classic Symptom Triad

The hallmark of MALS is the triad of postprandial abdominal pain, weight loss, and nausea or vomiting. These symptoms typically worsen after eating, as increased blood flow demands in the gut exacerbate the underlying vascular compression 1,2,3,4.

Variable and Overlapping Presentations

• Epigastric Pain: Most patients report upper abdominal pain, which may radiate to the back or flanks. The pain often appears after meals but can also occur during physical activity or even at rest 1,2,3.
• Gastrointestinal Distress: Nausea, vomiting, and bloating are frequent. Some patients experience delayed gastric emptying, resulting in a prolonged feeling of fullness 6.
• Weight Loss: The combination of pain and fear of eating often leads to unintended weight loss, which can be significant over time 1,2,3,4.
• Rare Symptoms: A minority experience fever, diarrhea, or positional pain unrelated to meals 4,8.

Mimicking Other Conditions

The non-specific nature of these symptoms means MALS often masquerades as more common gastrointestinal disorders, such as irritable bowel syndrome, peptic ulcer disease, or even gallbladder pathology 4,7. This frequently results in delayed diagnosis, with patients undergoing extensive evaluations before MALS is considered.

Types of Median Arcuate Ligament Syndrome

While MALS is generally discussed as a single clinical entity, there are important distinctions in its presentation and underlying anatomy. Understanding these subtypes aids clinicians in tailoring diagnosis and management strategies.

Type/Variant	Features/Presentation	Distinguishing Factors	Source(s)
Classic MALS	Postprandial pain, weight loss, nausea	Celiac artery compression by MAL	1,2,3,7,13
Neurogenic Type	Pain may be more neuropathic, less ischemic	Compression of celiac plexus/ganglia	5,1
Vascular/Ischemic	Severe pain, risk of aneurysm	Prominent vascular compression, possible aneurysm	2,9
Associated Syndromes	Symptoms overlap with other rare disorders	Ehlers-Danlos, POTS, delayed gastric emptying	6

Table 2: Variants and Types

Classic (Vascular) MALS

This is the most frequently recognized form, characterized by the classic triad and demonstrable celiac artery compression. It is primarily due to mechanical obstruction of blood flow 1,2,3.

Neurogenic (Neural Compression) MALS

Some patients exhibit symptoms attributable more to nerve (celiac plexus) compression than pure ischemia. These individuals may have pain out of proportion to vascular findings, and pathology studies reveal perineural fibrosis and nerve fiber proliferation 5,1. This supports the use of the more encompassing term "MALS" over "celiac artery compression syndrome."

Vascular Complications

A subset of patients may develop life-threatening complications such as aneurysms (notably of the gastroduodenal artery) due to altered blood flow dynamics 2,9. These cases can present acutely with hemorrhage.

Associated Syndromes

Recent studies have uncovered associations with other rare conditions, including:

• Delayed gastric emptying
• Connective tissue disorders (e.g., Ehlers-Danlos syndrome)
• Postural Orthostatic Tachycardia Syndrome (POTS) These associations suggest a broader spectrum of MALS and a possible genetic or systemic predisposition 6.

Overlapping and Atypical Presentations

Some patients may have combined features, such as both vascular and neurogenic symptoms, or present with unusual patterns like pain with exertion or in specific body positions 2,12. There is also overlap with superior mesenteric artery syndrome in rare cases 11.

Causes of Median Arcuate Ligament Syndrome

MALS is rooted in anatomic, vascular, and possibly neurogenic abnormalities. Understanding the mechanisms behind this syndrome is essential for accurate diagnosis and informed treatment choices.

Cause/Mechanism	Description	Impact on Symptoms	Source(s)
Anatomic Compression	Low-lying MAL compresses celiac artery	Reduced blood flow, ischemia	1,2,3,7
Neural (Celiac Plexus) Compression	Fibrotic tissue encases nerves	Neuropathic pain, GI symptoms	5,1
Respiratory Variation	Compression may worsen with expiration	Variable symptoms, diagnostic clue	2,3,4,7
Associated Disorders	Connective tissue, vascular anomalies	Increased risk, symptom diversity	6

Table 3: Causative Mechanisms

Anatomic Factors

The primary cause of MALS is an unusually low insertion of the median arcuate ligament, causing it to cross over and compress the celiac artery. This compression is often most pronounced during expiration, due to the upward movement of the diaphragm 1,2,3,7.

• Congenital or developmental: Most cases are due to anatomical variation—some individuals naturally have a lower ligament or higher origin of the celiac artery.
• Respiratory Influence: The degree of compression often changes with breathing; imaging during inspiration and expiration can reveal this dynamic 2,3,4.

Vascular Ischemia

Compression leads to narrowing (stenosis) of the celiac artery, reducing blood supply to the stomach, liver, and spleen, especially after meals when demand is increased. This ischemia is believed to be the main driver of postprandial pain and weight loss 1,2,3.

Neurogenic Contribution

Recent evidence points to neural involvement—specifically, compression and fibrosis of the celiac plexus and surrounding ganglia 5. This may explain pain that is not strictly related to blood flow and why some patients benefit from nerve block procedures 5,8.

Associated and Predisposing Conditions

• Connective Tissue Disorders: Ehlers-Danlos syndrome and similar conditions can predispose individuals to vascular and ligamentous abnormalities 6.
• Vascular Anomalies: Some patients have anatomical variations in their visceral arteries, potentially worsening or mimicking MALS 6.

Pathophysiologic Uncertainty

Despite these known mechanisms, the exact reasons why some with celiac artery compression develop symptoms while others do not remain unclear. There is no consensus on strict diagnostic criteria, and it is likely that multiple factors—including anatomy, neural involvement, and associated disorders—interact to produce the clinical syndrome 1,3,4,7.

Treatment of Median Arcuate Ligament Syndrome

Managing MALS is challenging due to its variable presentation and uncertain pathophysiology. However, advances in surgical and minimally invasive techniques have improved outcomes for many patients.

Treatment Approach	Description/Method	Indications/Outcomes	Source(s)
Surgical Decompression	Open, laparoscopic, robotic release of MAL	Mainstay, effective in most	1,2,3,4,7,10,11,13
Celiac Ganglionectomy	Removal of celiac plexus/ganglion	For neurogenic symptoms	1,5,7
Vascular Reconstruction	Bypass, patch, or stent for fixed stenosis	For persistent/recurrent stenosis	2,9,10
Endovascular Angioplasty/Stenting	Balloon dilation, stent placement	Adjunct or for complex cases, not first-line	1,2,7,9
Nerve Block	Celiac plexus block	For diagnosis or non-surgical management	5,8
Nonoperative/Conservative	Observation, symptom management	Limited efficacy	3,12

Table 4: Treatment Modalities

Surgical Decompression

The primary goal is to relieve the compression of the celiac artery and nerves by dividing (cutting) the median arcuate ligament. This can be achieved via:

• Open Surgery: Traditional, effective, but more invasive 2,10.
• Laparoscopic Surgery: Minimally invasive, shorter hospital stay, similar symptom relief as open 4,10,11,13.
• Robotic-Assisted Surgery: Offers precision, especially in complex cases 1,10,13.

Most patients experience significant, and often immediate, symptom relief following surgery—up to 85% report improvement 10,13. Long-term success is highest in those with severe vascular compression 11.

Celiac Ganglionectomy

Often performed in conjunction with decompression, this involves removal of the celiac plexus to address neurogenic pain. It is particularly useful in those with evidence of nerve involvement 1,5,7.

Vascular Reconstruction

For patients with persistent arterial narrowing or fixed stenosis after decompression, vascular procedures such as bypass or patch angioplasty may be necessary 2,9,10. In some cases, stent placement is added if blood flow is not adequately restored.

Endovascular Angioplasty and Stenting

Although these techniques can widen a narrowed artery, they do not address the underlying external compression. As such, they are typically reserved for adjunctive use or for patients with recurrent symptoms after surgical release 1,2,7,9.

Nerve Block and Nonoperative Management

Celiac plexus block can be used for diagnosis or temporary relief, especially in patients who are not surgical candidates 5,8. Purely conservative management is associated with poorer outcomes, with most patients experiencing persistent or worsening symptoms 3,12.

Choosing the Right Treatment

Due to the rarity and complexity of MALS, there are no universally accepted guidelines. Treatment must be individualized, taking into account the severity of symptoms, anatomical findings, and patient comorbidities 2,4,7.

Conclusion

Median Arcuate Ligament Syndrome is a complex, multifaceted disorder that can significantly impact quality of life. While rare, its hallmark symptoms—postprandial pain, weight loss, and nausea—should prompt consideration in patients with unexplained chronic abdominal complaints. Advances in imaging and surgical techniques have improved both diagnosis and management, but challenges remain.

Key takeaways:

• MALS presents with vague symptoms which often mimic other abdominal disorders, leading to delayed diagnosis 1,2,3,4,7.
• Types and presentations are variable, with both vascular and neurogenic mechanisms playing roles 5,6,9.
• Causes include anatomical, vascular, and neural compression, with possible contributions from associated syndromes like Ehlers-Danlos and POTS 1,2,5,6.
• Surgical decompression—open or laparoscopic—is the mainstay of treatment, providing symptom relief for most patients. Adjunctive procedures are sometimes necessary for complex cases 1,2,10,11,13.
• Individualized care is essential, as no single approach fits all patients, and multidisciplinary evaluation is often required 2,4,7.

With greater awareness and continued research, outcomes for patients with this rare syndrome are steadily improving, offering renewed hope for those who suffer from this elusive but treatable condition.