MRI of the pineal gland

Anatomy and physiology of the epithalamus

The epithalamus is an important region of the diencephalon, anatomically comprising several interconnected structures. It includes: the pineal gland (epiphysis), the habenula (habenula), habenular nuclei, habenular commissure, and striae medullares.

Special attention should be paid to the olfactory and autonomic functions mediated by the habenula and its nuclei. They function as a critical relay station for the entire olfactory system. Physiologically, this neural circuit plays a major role in ensuring the normal digestive process.

The reflex arc is structured as follows:

• Afferent olfactory fibers transmit the primary signal.
• The impulse travels to the striae medullares of the thalamus.
• Next, the signal is directed to the habenular nuclei.
• From there, efferent impulses reach the autonomic (salivatory) nuclei located in the brainstem.

Age-related changes and diagnostic imaging

The main structural unit of the pineal gland is specialized secretory cells — pinealocytes. From the perspective of diagnostic imaging, the epiphysis has a unique age-related feature that every clinician must remember.

Beginning approximately at the age of 15, the deposition of magnesium and calcium salts is initiated in the tissues of this gland. This physiological calcification causes the pineal gland to acquire marked radiopacity over time.

Historically, before the widespread clinical introduction of high-precision modalities such as computed tomography and magnetic resonance imaging, the clearly distinguishable shadow of the calcified epiphysis on plain skull radiography served as a crucial diagnostic landmark for physicians assessing potential shifts in midline brain structures.

Related MRI anatomy: a case study

When analyzing brain MRI scans, it is necessary to evaluate not only the pineal gland but also adjacent structures of the diencephalic region, particularly the basal ganglia and thalamus. As a demonstration, we will analyze a clinical case of thalamic pain syndrome.

Acute period of the disease: Patient is a 51-year-old male. The disease manifested with sudden nausea, severe throbbing headache, and presyncope. The patient noted a complete inability to stand without support. The ambulance crew recorded a blood pressure of 220/120 mm Hg and weakness in the left limbs.

Neurological status upon admission:

• Central left-sided hemiparesis with increased deep tendon reflexes on the left.
• Hypesthesia and hypalgesia (reduced pain sensitivity) near the midline on the left.
• Pallanesthesia — complete loss of vibratory sensation on the left.
• Mild proprioceptive sensory impairment on the left.

(As part of the differential diagnosis of such disorders, the presence of thermohypesthesia and astereognosis is also assessed).

Initial neuroimaging (brain CT) revealed a pattern of acute hemorrhage localized in the region of the basal ganglia on the right.

Catamnesis and the formation of pain syndrome

After 6 months of follow-up, the patient showed significant regression of left-sided hemiparesis and major sensory disturbances, with recovery of motor activity.

However, against this background, a severe pain syndrome began to develop. The patient started experiencing recurrent paroxysms of pain and dysesthesia in the left half of the body, strictly in the areas of prior hypesthesia. In character, these pathological sensations were compared by the patient to severe electric shocks.

Repeat neuroimaging: To clarify the cause, a brain MRI was performed. The tomogram visualized a small residual lesion represented by a cyst in the right thalamus — directly at the site of the previous hemorrhage.

Treatment and outcome: To manage the thalamic syndrome, it was necessary to prescribe a combination of medications: carbamazepine and amitriptyline, which produced a pronounced positive effect. Early attempts to discontinue drug therapy inevitably led to a relapse of pain paroxysms. Only after 3 years was it possible to gradually reduce the dosage of these drugs until complete cessation.

Class and exam questions

What else to study on this topic

• Pallanesthesia, hypalgesia, and objective sensory assessment methods
• Topical diagnosis of central hemiparesis
• Dynamics of hemorrhage lesions in the basal ganglia on CT and MRI
• Pathophysiology of thalamic pain syndrome
• Mechanism of action of amitriptyline and carbamazepine in neuropathic pain

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.