Revisiting nerve surgery with an emphasis of the brains response

1. Frontiers in Nerve Surgery
Vaikunthan Rajaratnam

2. Agenda
Module 6
Nerve Injuries and their Management
https://tinyurl.com/NERVE19
1. Volition and muscular action
2. Brain and plasticity
3. Peripheral strategies
4. Neuromuscular rehabilitation

3. 100 Billion

4. Grasp
Shoulder
Elbow
Hand

5. Human Volition
• generativity - capacity to trigger actions
• subjectivity - conscious experiences
associated with initiating voluntary actions
• teleology - goal-directed quality of
voluntary actions
Annu. Rev. Psychol. 2019. 70:9–28

6. The seat of motor action
• Area 4 the primary motor cortex, and Area 6 immediately forward of
Area 4
• Area 6 the premotor area (PMA) + signals of sensory components -
guide the movements of the body
• Supplementary motor area (SMA), in the inner part of Area 6, -
planning and execution of complex movements of both hands.
• This area together with the lower portion of the parietal lobe is where
the mirror neuron system
• “concept of command centers explicitly assumes that there exist within
the central nervous system many sources of commands to the motor
apparatus”

8. New neural pathways
• direct parietal connections to spinal interneuron
pools,
• enabling modulation of spinal circuits for goal-
directed actions of the hand and arm,
• supplementing the more traditional direct frontal
motor pathways
Jean-Alban Rathelot, Richard P. Dum, Peter L. Strick, Proceedings of
the National Academy of Sciences Apr 2017, 114 (16) 4255-4260

9. s
Lancet. 2017 May 6;389(10081):1821-1830.
implanted into the hand area on the
precentral gyrus of his motor cortex
percutaneous muscle-
stimulating electrodes
FES system - external stimulator -
biphasic, constant-current stimulation -
produce muscle contractions and
subsequent limb movement

11. S

12. Neuroplasticity
Hebbian Learning
increase in synaptic efficacy arises from
a presynaptic cell's repeated and persistent
stimulation of a postsynaptic cell
Proceedings of the National Academy of Sciences
Nov 2015, 112 (45) E6224-E6232

13. Extensive rewiring processes affecting population-wide
connectivity patterns after periods of induced neuronal inactivity
DENSIFICATION & STRENGTHENING

14. Scientific Reports | 7: 11724 |
increased synapse size , postsynaptic receptor concentration, increases action potential propagation probability
across an entire neuronal network, synaptic sensitivity, increased number of connections, unused neurons
become reconnected, sprouting of new dendritic spines during neuronal silencing.

15. Peripheral Nerve
Regeneration
Dodla MC, Alvarado-Velez M, Mukhatyar VJ,
Bellamkonda RV. Chapter 69 - Peripheral Nerve
Regeneration. In: Atala A, Lanza R, Mikos AG,
Nerem R, editors. Principles of Regenerative
Medicine (Third Edition Boston: Academic Press;
2019)

16. Review of
Biofabrication
Strategies

17. Sulaiman OAR, Gordon T. A rat study of the use of end-to-side peripheral nerve repair as a “babysitting” technique
to reduce the deleterious effect of chronic denervation. Journal of Neurosurgery 2018 Sep 14 [cited 2019 Aug
30];131(2):622–32.

18. Repair digital nerves or not?
Dunlop RLE, et al. BMJ Open 2019;9:e025443

23. Lack of high-quality evidence to support
surgical repair of digital nerve injuries in adults

24. SPASTICITY

25. Dr Fox Effect
Ignorance is bliss
• contralateral C7 nerve transfer .... remains
controversial because…. the inherent challenges
of the long distance and time needed for
……and the degree of cortical reorganization
required.
• distal muscles are functionally reinnervated in
such a short time seems unlikely to us.
• alternative hypothesis to explain the functional
improvement is that there was reduction in
spasticity caused by the C7 neurotomy
• improvement in function at 10 months cannot
be readily explained
N Engl J Med 2018; 378:83-84

26. Spasticity and Energy
• movement speed that minimizes energetic
cost
• Reward makes it worthwhile to be
energetically inefficient
• Effort may be represented objectively via
energetic cost and discounted in time
• Neural control of decisions and movements
may share a common utility

27. Rehabilitation
Glenn Nielsen, Marta Buszewicz, Mark J Edwards & Fiona Stevenson (2019): A qualitative study of the experiences and perceptions of patients with
functional motor disorder, Disability and Rehabilitation

29. Mirror neuron
systems
• active during goal-directed action
and while observing the same
motor act
• meaning of a motor act (action
understanding) is represented in
this “mirror neuron system”
(MNS).
• ability to observe and accurately
imitate
• activated when an action is
executed, observed, anticipated or
imagined
• activated during kinaesthetic
imagery

30. Rehabilitation drives structural adaptations in
neurons to enhance recovery after brain injury
Enabled by acetylcholine

31. • (i) stimulation-based priming,
• (ii) motor imagery and action observation,
• (iii) sensory priming,
• (iv) movement-based priming, and
• (v) pharmacological priming.

32. Novel long-term motor learning
effects with
• tDCS and
• motor practise post-stroke.

33. Robotic Neuromuscular
Rehabilitation
• AS A VEHICLE TO TRANSLATE INTENSITY INTO A
STROKE REHABILITATION PROGRAM
• TO EXPLORE THE EFFECTIVENESS OF THE TYPE OF
ASSISTANCE
• TOOL TO ALTER EXPERIMENTAL CONDITIONS
• OBJECTIVE EVALUATION TOOL AFFORDING INSIGHTS
INTO MOTOR RECOVERY PROCESS
• ENABLING THE REHABILITATION PROCESS
Duret, C., Grosmaire, A. G., & Krebs, H. I. (2019). Robot-Assisted Therapy in Upper
Extremity Hemiparesis: Overview of an Evidence-Based Approach Frontiers in
neurology, 10, 412.

34. https://tinyurl.com/STROKE2020
Okinawa, 10 – 12 December 2020