Differential Diagnosis for Weakness with Shoulder, Paresthesia around Bicep, and Pain around Shoulder
Single Most Likely Diagnosis
- Thoracic Outlet Syndrome (TOS): This condition involves compression of the nerves and/or blood vessels that pass into the thoracic outlet (the space between your collarbone and first rib). It can cause shoulder and arm pain, weakness, and paresthesia, which aligns with the symptoms described. The absence of trauma and a negative cervical MRI makes TOS a plausible explanation, as it doesn't necessarily involve cervical spine pathology.
Other Likely Diagnoses
- Brachial Plexitis (Neuralgic Amyotrophy): An inflammatory condition affecting the brachial plexus, which can cause severe pain, usually around the shoulder, followed by weakness and atrophy of the affected muscles. Paresthesia can also occur. This condition can occur without trauma and might not be visible on a cervical MRI.
- Rotator Cuff Tendinopathy or Tear: While more commonly associated with pain and weakness, significant rotator cuff pathology could potentially cause paresthesia due to mechanical irritation of nearby nerves. The absence of trauma doesn't rule out this condition, as it can result from chronic overuse.
- Suprascapular Neuropathy: This involves compression of the suprascapular nerve, which can cause shoulder pain and weakness, particularly of the supraspinatus and infraspinatus muscles. Paresthesia around the bicep could be a referred symptom.
Do Not Miss Diagnoses
- Pancoast Tumor: A type of lung cancer located at the top of the lung that can invade the brachial plexus, causing shoulder pain, weakness, and paresthesia. Although rare, missing this diagnosis could be fatal.
- Multiple Myeloma or Other Systemic Diseases: Certain systemic diseases can cause bone lesions that might not be evident on a cervical MRI but could affect the shoulder and arm, leading to the described symptoms.
- Vascular Conditions (e.g., Subclavian Artery Thrombosis): While less likely, vascular conditions affecting the arm could potentially cause pain, weakness, and paresthesia, especially if there's significant compromise of blood flow.
Rare Diagnoses
- Hereditary Neuropathy with Liability to Pressure Palsies (HNPP): A genetic condition that makes nerves more susceptible to compression, which could potentially cause the described symptoms.
- Idiopathic Brachial Plexitis in the Context of another Systemic Condition: Certain autoimmune or inflammatory conditions could potentially cause brachial plexitis or neuropathy, leading to the symptoms described.