Vestibulospinal, reticulospinal and descending propriospinal nerve fibres in man

Abstract

The course and location of vestibulospinal, reticulospinal and descending propriospinal fibres in man are reported. The investigation was carried out on three patients with supraspinal lesions, four with transection of the spinal cord and 33 with anterolateral cordotomies. The lateral vestibulospinal tract at the medullospinal junction and in the first three cervical segments lies on the periphery of the spinal cord lateral to the anterior roots. It moves to the sulcomarginal angle in the remaining cervical segments. In the thoracic cord, it moves laterally, being traversed by the most lateral of the anterior roots. Reticulospinal fibres descend bilaterally in the spinal cord with a preponderance of ipsilateral fibres. Reticulospinal fibres in general do not form well-defined tracts, but are scattered throughout the anterior and lateral columns. They are intermingled with propriospinal fibres and with ascending and descending fibres of other systems. Most reticulospinal fibres move posterolaterally as they descend. It follows that fibres from the brainstem that enter the cord in the anterior column may be in the lateral column anterior to the lateral corticospinal tract at lower levels. Reticulospinal fibres within the lateral column lie anterior to the lateral corticospinal tract. They consist of scattered fibres between the lateral horn and the periphery, most of them in the medial two-thirds of the column. In addition, they are present in a more compact group, forming a triangle on transverse section on the periphery of the lateral column, immediately anterior to the lateral corticospinal tract. On the periphery of the anterior and anterolateral columns reticulospinal fibres descend as small groups or as a continuous band of fibres. The most medial of these reaches the sacral segments and is included in the sulcomarginal fasciculus. A compact group of fibres, shown previously to be central sympathetic fibres ending in the intermediolateral and intermediomedial cell columns, surrounds the lateral horn. They do not extend throughout the thoracic cord in all cases. Anterior to this group is another group of fibres lying on the anterolateral surface of the anterior horn. As these fibres were degenerating following a pontine lesion, they must be reticulospinal fibres. The fibres were not seen in all cases and they did not always reach the lowest thoracic segments. Reticulospinal fibres enter the grey matter in the zona intermedia and along the anterolateral and anterior surfaces of the anterior horns. Caudal to the cervical enlargement, the number of reticulospinal fibres decreases, and their place is taken by propriospinal fibres. But they are not totally replaced by the propriospinal fibres, for reticulospinal fibres continue down into the lowest sacral segments. Of the propriospinal fibres, the majority are short: descending fibres within the juxtagriseal layer are one to two segments long or less.

Independent spinal cord atrophy measures correlate to motor and sensory deficits in individuals with spinal cord injury

“…Sensory pathways are dominantly located in the posterior and anterior parts of the spinal cord white matter, whereas motor pathways are dominantly located more laterally. 9,10 Our hypothesis was that atrophy in the antero-posterior parts would be well correlated to sensory deficits, whereas atrophy in the left-right parts would be better correlated to motor deficits (see Figure 1a). Our aim was to introduce robust, sensitive and specific parameters to evaluate the functional state of individuals with SCI.…”

Coordination of Locomotion with Voluntary Movements in Humans

“…The spinal networks responsible for the locomotion timing pattern are likely to be distributed across several spinal segments linked by long propriospinal connections [as suggested by Nathan et al (1996)] including both descending and sensory inputs (Kiehn et al, 1998;Orlovsky et al, 1999;Dietz, 2002). Some evidence for this may be seen in spinal cord injury patients with both complete and incomplete spinal transections (Ivanenko et al, 2003).…”

Coupling of upper and lower limb pattern generators during human crawling at different arm/leg speed combinations

“…In the human, the major locus of CPG circuitry is in the lumbosacral enlargement and coupling of cervical and lumbosacral CPGs may depend on the strength of propriospinal connections. Indeed, cervical and lumbosacral enlargements in humans appear to be coupled by long propriospinal neurons projecting to different pools of alpha motor neurons across several spinal segments (Nathan et al 1996). Moreover, reflex studies have suggested that stimulation of upper limb nerves can influence lower limb muscle activation during rhythmic activity and vice versa (Haridas and Zehr 2003;Zehr et al 2004).…”