Tactile agnosia

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at October 15, 2016
StartDiseasesTactile agnosia

Tactile agnosia refers to the inability to identify an object from touching it. It's also known by the name astereognosis. Tactile agnosia doesn't involve a loss of sensitivity in the nerves of the hand; for example, the ability to touch and sense hot versus temperatures still functions. Tactile agnosia is a failure of perception.


Definition & Facts

The parietal lobe is the portion of the cerebral cortex that processes information picked up from our senses. Damage to the parietal lobe by infection, concussion, or tumor growth can impact how our brains process information that comes in from our eyes, ears, nose, tongue, and skin.

Agnosia, generally, is defined as the inability to sense input or information that could be picked up by the five senses. Varieties of agnosia include visual agnosia (sight), auditory agnosia (sound), olfactory agnosia (smell), gustatory agnosia (taste), and tactile (touch).

Agnosia is caused by damage to the parietal lobe. In addition to conditions such as tactile agnosia, parietal lobe damage can manifest as disabilities in spatial understanding, reaching for and grasping objects accurately, and the ability to recall sensory memories.

Depending on the portion of the parietal lobe that has suffered damage, personality changes can occur. Patients are unable to process familiar objects by touch and need to make a visual connection to the object to remember the name of the item they are holding.

Symptoms & Complaints

Those who suffer from tactile agnosia may recognize an object by sight, but cannot recognize it by touch. They are unable to make the connection between the item they're feeling and the memory of the item held in the brain.

This is due to a disconnect between the nerves of the hand and the portion of the brain that recognizes stimulation from the fingertips. The memory is still there, but is inaccessible. The parietal lobe is critical in converting stimuli from the senses into memories and thoughts that can be used to define familiar objects.


Tactile agnosia or astereognosis is caused by damage or lesions on the parietal lobe. The parietal lobe is part of the cerebral cortex and is found toward the back of the brain. It's how we process information from things we touch and taste, and helps us to determine the temperature of things we handle or place in our mouths.

Damage to the parietal lobe, caused by traumatic brain injury, stroke, brain hemorrhage, growths such as benign tumors or malignant tumors, and illness can all impact the functioning of the parietal lobe.

Infection causing the pressure on the brain need not occur inside the skull cavity. Infections such as tooth abscesses and sinus conditions can greatly increase the pressure inside the the skull. Brain infection often manifests as an abscess, and can lead to tremendous skull pressure and damage to the brain tissue. Toxic exposure can also lead to damage to the parietal lobe and conditions such as tactile agnosia.

Diagnosis & Tests

The simplest test for astereognosis is to have the patient handle a familiar object with their eyes closed. Patients with this condition will not be able to identify the object by touch alone, though they will recognize it by sight. Determining the patient's medical history regarding brain injuries, illness, and exposure to environmental toxicants is critical.

Anyone suffering from symptoms should be assessed for toxic contaminants including carbon monoxide, pesticides, metals including lead and solvents. While removing the patient from proximity to the toxin may limit the amount of long-term damage, careful review of their blood chemistry and brain make-up must be undergone to confirm the risks of long-term damage to the parietal lobe.

Finally, computed tomography (CT) scans and magnetic resonance imaging (MRI) studies can help determine the source and severity of damage to the parietal lobe. 

Treatment & Therapy

Depending on the source of the damage to the parietal lobe, treatment can include antibiotics to reduce inflammation in the skull caused by brain abscess or inflammation from infection.

Benign and malignant growths can be removed by surgery or chemotherapy. Brain tissue lost to traditional stroke, caused by blood clots and leading to hypoxia will not rejuvenate.

If the parietal lobe is being impacted by a bleeding blood vessel, surgery to cauterize the vessel may help the condition. If brain damage stems from traumatic injuries including concussions, treatment options may involve bed rest.

Prevention & Prophylaxis

Avoiding head injuries is critically important from birth to death if we intend to maintain a healthy cognitive state. Recent data from the American Academy of Neurology indicate that even mild concussion can generate microscopic brain lesions visible on MRI. While not all of these injuries may be permanent, protecting the skull from direct hits and violent movements which jar the brain is crucial to maintaining brain health.

Additionally, many brain lesions often stem from stroke. Many people with a family history of high blood pressure, a common indicator for stroke, can reduce their risk by maintaining a healthy weight and exercise regimen.

Lowering salt intake and incorporating additional walking into all daily activities will reduce the risk of high blood pressure and can help keep both one's stress level and weight at a healthy level. Both strokes from blood clots and hemorrhagic stroke can cause long term brain damage.

Should one's blood pressure remain stubbornly high after dietary and exercise adjustments, careful monitoring and medication of the condition may be necessary. By staying on top of your blood pressure numbers, a person can increase their chances of enjoying long term brain health.

Infections in the skull and jaw area can cause abscess, swelling and pressure in other areas of the skull. Practicing good dental hygiene and addressing sinus infections and abnormalities are important to maintain brain health. If a person notices problems with balance or lose the ability to judge how to easily pass through doorways, they should contact their physician to confirm they're not suffering from sinus inflammation or an ear infection.