Cervical Spondylosis with Radiculopathy: This condition is a common cause of neck pain and radiculopathy (tingling, numbness, or weakness) in the arms, especially in individuals over 60 years old. The new pillows may have altered the patient's sleeping position, exacerbating a pre-existing condition. The symptoms on the left side of the neck and tingling on the right thumb suggest cervical nerve root impingement, which is consistent with this diagnosis.

Muscle Strain: The introduction of new pillows could lead to an awkward sleeping position, resulting in muscle strain in the neck. This strain could cause pain on one side of the neck and potentially refer pain or cause tingling sensations in the arm due to muscle tension.
Cervical Disc Herniation: Similar to cervical spondylosis, a herniated disc in the cervical spine could compress nerve roots, leading to pain on one side of the neck and tingling or numbness in the arm or hand. The onset after using new pillows might coincide with a new or exacerbated disc herniation.
Thoracic Outlet Syndrome: 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 neck pain and tingling in the arms or hands, although it's less likely given the specific distribution of symptoms.

Cervical Spinal Stenosis: A narrowing of the spinal canal in the neck, which can compress the spinal cord or nerve roots, leading to pain, weakness, or tingling in the neck, arms, or legs. It's crucial to identify this condition due to the potential for severe neurological deficits if left untreated.
Stroke or Transient Ischemic Attack (TIA): Although less likely given the description, it's essential to consider vascular events, especially in a 64-year-old patient. Neck pain and arm tingling could be atypical presentations of a stroke or TIA, particularly if there are other risk factors or symptoms present.
Multiple Sclerosis: An autoimmune disease that affects the brain and spinal cord, leading to a wide range of neurological symptoms, including numbness, tingling, and pain. Early diagnosis is critical for managing the disease.

Cervical Artery Dissection: A tear in one of the arteries in the neck, which can lead to a stroke. It might present with neck pain and neurological symptoms, including tingling.
Tumors (Benign or Malignant): Although rare, tumors affecting the cervical spine or nerves can cause neck pain and neurological symptoms like tingling. These would typically have a more gradual onset and might be accompanied by other systemic symptoms.
Infections (e.g., Abscess, Osteomyelitis): Infections of the cervical spine can cause severe neck pain and neurological symptoms. These conditions are less common and usually present with additional symptoms like fever, chills, or recent trauma.