Blocq's disease

Blocq's syndrome
Trunk sway, path deviation, arm swing
Anatomical terminology []

Blocq's disease was first considered by Paul Blocq (1860–1896), who described this phenomenon as the loss of memory of specialized movements causing the inability to maintain an upright posture, despite normal function of the legs in the bed. The patient is able to stand up, but as soon as the feet are on the ground, the patient cannot hold himself upright nor walk; however when lying down, the subject conserved the integrity of muscular force and the precision of movements of the lower limbs. The motivation of this study came when a fellow student Georges Marinesco (1864) and Paul published a case of parkinsonian tremor (1893) due to a tumor located in the substantia nigra.

In the third paper published by Paul Blocq, he was trying to determine the neurophysiology behind this disease by relating the cerebral cortex (the decision making) and the spinal cord (the decision executer). His hypothesis was that there would exist an inhibitory influence which exerted and influenced the cortical or spinal centers for standing and walking.

One of the issues that neurobiologists are more concerned is related with the ability of learning and retaining motor skills controlled by the primary motor cortex. Through literature, they have found that primary motor cortex neurons may control skill acquisition and retention. One of the abilities of the motor cortex that allow this control is plasticity which occurs due to the everyday experience of movement repetition. A common substrate of plasticity are the internal system of connections that are located around these regions, creating motor maps.

Vestibulospinal tracts: The importance is involved in the control of postural adjustments and head movements as well as balance maintenance. Any movement of the body is detected by the vestibular sensory neurons, and the sensory motor replies by counteracting the movements through the vestibulospinal tracts and exerting action on a group of muscles throughout the body. The lateral vestibulospinal tract excites antigravity muscles in order to exert control over postural changes necessary to compensate for tilts and movements of the body. The medial vestibulospinal tract innervates neck muscles in order to stabilize head position as one moves around the world.

Reticulospinal tracts: It serves as a connector for the corticospinal system by which cortical neurons can control motor function. These tracts regulate the sensitivity of flexor responses to ensure that only noxious stimuli elicit the responses. The reticular formation also contains circuitry for many complex actions, such as orienting, stretching, and maintaining a complex posture. Commands that initiate locomotor circuits in the spinal cord are also transmitted through the medullary reticulospinal tract. Thus, the reticulospinal tracts are involved in many aspects of motor control, including the integration of sensory input to guide motor output.