Imaging Findings

Based on the provided MRI images, a cystic lesion can be observed around the glenoid rim of the shoulder joint, appearing as high signal intensity on T2-weighted sequences with a well-defined cystic nature (as seen in both sagittal and axial views). The lesion is adjacent to the glenoid labrum, where mild irregularity or signs of labral tear may be present. The cyst is located near the suprascapular notch, potentially exerting pressure on the suprascapular nerve passing through this area. The affected region is close to the supraspinatus and infraspinatus tendons, but there is no obvious evidence of a complete tendon rupture. The rotator cuff tendons may exhibit mild abnormal signal, suggesting tendon wear or a partial tear.

Potential Diagnoses

1. Glenoid labrum tear with paralabral cyst (Paralabral cyst):
   Caused by joint fluid leaking through a tear in the labrum or joint capsule, commonly seen in the pathway of the suprascapular nerve (which innervates the supraspinatus and infraspinatus muscles), potentially leading to nerve compression and resulting in shoulder pain and restricted range of motion.
2. Partial rotator cuff tear or tendinopathy:
   Repetitive shoulder loading, abduction, and rotation can lead to chronic wear or partial tearing of the cuff tendons. On MRI, changes in tendon signals near their insertion or within the tendon itself may be noted, clinically presenting as pain on shoulder movements.
3. Subacromial impingement syndrome (listed as differential):
   Although primarily involving the subacromial space, it should be considered in individuals who frequently use shoulder abduction movements, as subacromial impingement or subacromial bursitis can also cause shoulder pain.

Final Diagnosis

Considering the 18-year-old male patient’s shoulder pain during abduction and external rotation, the MRI findings of a cystic lesion around the glenoid and possible labral tear, as well as signs of compression in the suprascapular nerve region, the most likely diagnosis is: “Glenoid labrum tear with a paralabral cyst (Paralabral cyst), possibly accompanied by mild rotator cuff injury.” If the exact location and extent of the cyst and labral tear need further clarification, additional shoulder arthrography or arthroscopic evaluation may be considered.

Treatment Plan and Rehabilitation

Taking into account the patient’s young age, interest in weight training, and imaging findings suggesting a labral tear and paralabral cyst with possible nerve compression, treatment can be divided into:

1. Conservative Treatment:
   For milder symptoms or acute flares that are not severe, initial management can include shoulder immobilization, non-steroidal anti-inflammatory drugs (NSAIDs), and local physical therapy (such as ultrasound therapies, warm compresses, and muscle coordination training). Rehabilitation focuses on restoring shoulder joint stability and the strength of the rotator cuff muscles, while avoiding excessive loading to prevent re-injury.
2. Arthroscopic Surgery:
   In cases of persistent pain, significant functional impairment, or confirmed severe labral tear with a noticeably compressive paralabral cyst, arthroscopic surgery may be required to repair the torn labrum and drain or remove the paralabral cyst.

Rehabilitation Training (FITT-VP Principle):
1. Frequency: 3–4 times per week of shoulder stability and control training.
2. Intensity: Start with light resistance (e.g., resistance bands, small dumbbells) and gradually increase the load, avoiding pain.
3. Time: Each session should last 20–30 minutes, including warm-up and cool-down.
4. Type: Focus on resistance training for the muscles around the shoulder (especially the supraspinatus, infraspinatus, teres minor, and scapular stabilizers), joint mobilization techniques, and proprioception exercises. Gradually increase the angle of shoulder abduction and external rotation.
5. Volume & Progression: Gradually increase resistance and range of motion based on pain and muscle strength recovery. Conduct a phase assessment every 2–4 weeks to adjust training. Avoid sudden increases in load to prevent secondary injuries.

Precautions:
- In the presence of any acute inflammation or significant worsening of pain, reduce or suspend training and consult a physician.
- If there is notable weakness or persistent nocturnal pain, early MRI or arthroscopic evaluation is recommended.
- Maintain good posture and proper alignment of the shoulder joint to avoid excessive compensation that may harm other structures.

Disclaimer

This report is solely a reference-based medical analysis derived from the current imaging and clinical information. It cannot replace in-person medical consultation or professional medical advice. If you have any questions or if your condition changes, please consult a healthcare professional and follow their guidance.