Cervicogenic Headache or Cervical Radiculopathy: This condition occurs due to compression or irritation of the cervical nerves, which can happen when bending over, leading to symptoms like tingling or numbness in the head, including the top of the skull. The mechanism involves the stretching or compression of nerves in the neck, which can cause referred pain or sensations to the head.

Tension Headache: Tension headaches can cause a band-like sensation around the head and may lead to tingling sensations, especially if there is significant muscle tension in the neck and scalp.
Occipital Neuralgia: This condition involves the irritation of the occipital nerves, which can cause pain and tingling in the back and top of the head, exacerbated by certain movements like bending over.
Chiari Malformation: A structural defect in the cerebellum that controls balance, can cause symptoms like tingling in the head when bending over due to increased pressure on the brain and spinal cord.

Subarachnoid Hemorrhage or Other Intracranial Bleeds: Although less likely, any sudden onset of severe headache or tingling, especially if accompanied by other symptoms like confusion, vomiting, or loss of consciousness, could indicate a life-threatening condition like a subarachnoid hemorrhage.
Multiple Sclerosis: An autoimmune disease that affects the brain and spinal cord, can cause a wide range of neurological symptoms, including tingling sensations, especially if there are lesions in areas affecting the sensory pathways.
Cervical Spinal Stenosis: Narrowing of the spinal canal in the neck, which can compress the spinal cord or nerves, leading to various symptoms including tingling in the head when bending over.

Arnold-Chiari Malformation Type II: A more severe form of Chiari malformation that includes the displacement of the cerebellar tonsils and vermis into the foramen magnum, which can cause a variety of neurological symptoms.
Syringomyelia: A disorder in which a fluid-filled cavity or syrinx forms within the spinal cord, can cause tingling or numbness in parts of the body, including the head, especially if the syrinx affects the cervical spine.
Neurodegenerative Diseases (e.g., Friedreich's Ataxia): Certain neurodegenerative diseases can cause a wide range of neurological symptoms, including tingling sensations, though these would typically be part of a broader clinical picture involving progressive neurological decline.