Cervical Radiculopathy: This condition, often due to a herniated disk or bone spur, compresses or irritates a nerve root in the cervical spine, leading to paresthesias (tingling, numbness) in the arm. It's a common cause of arm paresthesias and typically presents with neck pain and specific patterns of sensory loss corresponding to the affected nerve root.

Thoracic Outlet Syndrome: Compression of the nerves and/or blood vessels that pass into the arm through the thoracic outlet (the space between your collarbone and first rib) can cause paresthesias, pain, and weakness in the arm. Symptoms can be exacerbated by certain movements or positions.
Carpal Tunnel Syndrome: Although more commonly associated with median nerve compression at the wrist, carpal tunnel syndrome can cause paresthesias in the hand and, less commonly, radiate up the arm. It typically affects the thumb, index, middle finger, and part of the ring finger.
Ulnar Neuropathy: Compression of the ulnar nerve, often at the elbow or wrist, can lead to paresthesias in the little finger and part of the ring finger, sometimes extending up the arm.

Stroke or Transient Ischemic Attack (TIA): Although less common, sudden onset of paresthesias in one arm can be a symptom of a stroke or TIA, especially if accompanied by other symptoms like facial weakness, speech difficulties, or leg weakness. Prompt recognition is crucial for timely intervention.
Multiple Sclerosis: An autoimmune disease that affects the brain and spinal cord, leading to a wide range of neurological symptoms, including paresthesias. While less common, it's a critical diagnosis not to miss due to its significant impact on the patient's quality of life and the availability of disease-modifying treatments.
Brachial Plexus Injury: Trauma to the brachial plexus, the network of nerves that conducts signals from the spinal cord to the shoulder, arm, and hand, can cause paresthesias, pain, and weakness in the arm. This diagnosis is particularly important in the context of trauma.

Vitamin Deficiencies (e.g., Vitamin B12 Deficiency): Certain vitamin deficiencies can cause neurological symptoms, including paresthesias. While less common, these deficiencies can be easily treated with supplementation, making them important to consider in the differential diagnosis.
Peripheral Neuropathy: A result of damage to the peripheral nerves, often caused by diabetes, but also by other conditions such as amyloidosis, or certain infections and exposures. It can cause a variety of symptoms, including paresthesias, typically in a stocking and glove distribution but can be more localized.
Tumors: Both benign and malignant tumors can compress nerves, leading to paresthesias. Examples include schwannomas, neurofibromas, and Pancoast tumors (located at the apex of the lung).