What is the diagnosis and treatment approach for a patient with brachial plexopathy, considering the underlying cause and extent of damage?

Brachial Plexopathy: Diagnosis and Treatment

Diagnostic Approach

MRI of the brachial plexus with and without IV contrast is the gold standard imaging modality and should be ordered first when brachial plexopathy is suspected, as it provides superior soft-tissue visualization with 81% sensitivity, 91% specificity, and 88% accuracy. 1, 2

Clinical Localization

• Pain, weakness, and sensory loss occur across multiple peripheral nerve distributions in the shoulder and arm, distinguishing plexopathy from radiculopathy which follows a single dermatome 2
• Flaccid weakness affects regions innervated by multiple nerves from the affected plexus, with loss of tendon reflexes in those regions 2
• Symptoms cross multiple dermatomes rather than following a single nerve root distribution 2

Electrodiagnostic Confirmation

• Clinical diagnosis must be confirmed by electrodiagnostic studies showing abnormalities in multiple nerve distributions 2, 3
• EDX testing defines localization, pathophysiology, chronicity, severity, and prognosis 3

Imaging Protocol Specifications

• Use dedicated brachial plexus MRI protocols with orthogonal views through the oblique planes of the plexus, including T1-weighted, T2-weighted, fat-saturated T2-weighted sequences, STIR sequences, and fat-saturated T1-weighted postcontrast sequences 4, 5
• Standard neck, chest, or spine MRI protocols are inadequate and will miss plexus pathology 4, 5
• MRI provides additional diagnostic information beyond clinical evaluation and electrodiagnostic studies in 45% of patients 1, 5
• For traumatic cases, delay imaging until approximately 1 month post-injury to allow hemorrhage and edema resolution 4, 5

Alternative Imaging When MRI Contraindicated

• CT neck with IV contrast offers the next highest level of anatomic visualization after MRI 1, 4
• Use 1.5 Tesla MRI when metal is present in the area to reduce artifact 4, 5

Etiologic Classification and Treatment

Neoplastic Causes

Superior sulcus tumors (Pancoast tumors) and breast cancer metastases are the most common malignant causes, typically affecting the lower trunk with ulnar distribution pain and potential Horner syndrome. 1

• Primary tumors are most commonly benign peripheral nerve sheath tumors (schwannomas and neurofibromas) 2
• Malignant peripheral nerve sheath tumors occur more frequently in neurofibromatosis type 1 2
• FDG-PET/CT is indicated when known malignancy or post-treatment syndrome is present 4

Inflammatory/Immune-Mediated Causes

Parsonage-Turner syndrome (neuralgic amyotrophy) is managed conservatively with physical therapy to maintain range of motion and monitoring for recovery. 4, 6

• Presents with acute onset severe pain followed by weakness, typically asymmetric around the shoulder girdle and arm muscles 6
• Other inflammatory causes include chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), multifocal motor neuropathy, and Lewis-Sumner syndrome 1, 2
• Diagnosis is primarily clinical and electrodiagnostic, as imaging features overlap considerably among inflammatory conditions 1

Traumatic Causes

Penetrating and open injuries require early surgical exploration, while blunt and closed injuries may be managed operatively or non-operatively based on severity. 4

• Distinguish preganglionic (root avulsion) from postganglionic injuries, as treatment approaches differ fundamentally 2, 5
• MRI can identify pseudomeningoceles as surrogate markers for root avulsion 5
• Complete nerve ruptures have worse outcomes and often require early operative management 4
• For compressive lesions with preserved nerve continuity, open fasciotomy and external neurolysis can provide significant pain relief (VAS reduction from 6.4 to 2.0, p<0.01) 7

Radiation-Induced Plexopathy

• Occurs as a delayed complication of radiation therapy 2
• MRI with contrast helps differentiate radiation-induced changes from tumor recurrence 1, 5

Other Causes

• Diabetic amyotrophy is the most common cause of lumbosacral plexopathy but can affect brachial plexus 8
• Sarcoidosis and infectious causes require specific serologic and imaging evaluation 1
• Hereditary neuropathies (Charcot-Marie-Tooth syndrome) may present with plexopathy features 1

Critical Diagnostic Pitfalls

• Do not order cervical spine MRI alone when plexopathy is suspected—it only evaluates nerve roots within and immediately adjacent to neural foramina, missing the plexus lateral to the foramina 1, 5
• In diagnostic uncertainty between radiculopathy and plexopathy, order both cervical spine MRI and dedicated brachial plexus MRI 2, 5
• CT myelography and CT cervical spine cannot visualize preganglionic nerve roots or fully evaluate the postganglionic plexus 1
• Rehabilitation programs must account for pain preceding and complicating motor recovery 2