Our patient, a 30-year-old doctor, was brought to the emergency department of an Indian Naval Hospital in an unresponsive state following a road traffic accident, was resuscitated as per ATLS (Advanced Trauma Life Support) guidelines, and intubated before regaining spontaneous cardiac activity after 15 minutes. A detailed secondary survey revealed a Glasgow Coma Scale score of E1M1VT, sluggishly reacting pupils, flaccid extremities, absent deep reflexes, and a mute plantar reflex; the patient was subsequently diagnosed with an unstable odontoid fracture (C1–C2 instability with left C1 lamina fracture) and cord compression (Fig. 1A–C), suggesting the existence of American Spinal Cord Injury Association (ASIA) grade A tetraplegia. On the fifth day postinjury, he underwent C1–C2 posterior stabilization (Goel’s procedure) as shown in Fig. 1D and was continued on positive-pressure ventilation. A tracheostomy was conducted on the third postoperative day in anticipation of prolonged MV. The patient improved hemodynamically without any neurological recovery but repeatedly failed attempts to wean him from MV. Six months later, he continued to be ventilator-dependent, tetraplegic with ASIA grade A, and bladder- and bowel-incontinent with a Spinal Cord Independence Measure (SCIM) III score of zero out of 100 points [14]. Possible modalities for weaning him from MV were explored and, with the available resources and technical expertise, DP with bilateral PNS implantation was planned.

The chosen procedure required an intact phrenic nerve that was identified preoperatively by ultrasonography (USG), with neck and nerve stimulation performed by a nerve stimulator under USG guidance [15,16]. Diaphragm jerk was identified visually and by observing diaphragm thickening on USG imaging of the lungs. Informed consent was obtained and stimulation lead implantation was performed with the patient in a supine position under general anesthesia (Fig. 2A). A skin incision was made as shown in Fig. 2B, extending from the lateral edge of the sternocleidomastoid muscle, followed by the creation of a subplatysmal flap and the identification of the C5, C6, and C7 spinal nerves. The phrenic nerve was then located, traversing the superior border of the scalenus medius muscle, and its integrity was assessed by monopolar electrical stimulation and the observation of contractions in the ipsilateral diaphragm. A quadripolar cylindrical electrode (Quadtrode; St. Jude Medical, Saint Paul, MN, USA) was placed along the right phrenic nerve (Fig. 3A) and tacked to the scalenus medius muscle. Successful placement of the electrode was confirmed intraoperatively by brisk downward deflection of the ipsilateral diaphragm, under fluoroscopy. A subcutaneous tunnel was created on the anterior chest wall to pass the proximal ends of the electrodes to the implantable pulse generator (IPG, Eon-Mini Rechargeable; St. Jude Medical), as shown in Fig. 3B, which was placed in a subcutaneous pocket made in the right hypochondrium (Fig. 3C). A similar operation was conducted on the contralateral side to secure the correct placement of the electrodes along the left phrenic nerve and confirm their connection to the IPG in the subcutaneous pocket over the right hypochondrium (Fig. 4), confirmed on a chest radiograph.

The IPG was switched on during the first postoperative day with an initial device setting in cyclic mode (composed of 1 second for ramp up, 2 seconds with the device on, and 3 seconds with the device off), a pulse width of 150 microseconds, a frequency of 21 Hz, and an amplitude of 2V. DP was initiated as per a standardized protocol [17,18] on the 10th postoperative day and diaphragm training was started (1.5–2 hr/day with an amplitude of 2.0 V). The voltage was increased by 0.5 V each week with a corresponding increased duration of training time. The amplitude of 4.5 V was found to adequately contract the diaphragm to achieve adequate tidal volume and no hypercarbia after up to 8 hours of pacing.

After 6 weeks of rehabilitation, intense patient counseling, and motivation, the level of ventilator dependence was reduced to only during the night. Then, a successful trial for spontaneous ventilation during the night was conducted at 12 weeks. At this point, however, the electrode on the left side was observed to be delivering inadequate impulses, resulting in an ineffective contraction of the left hemi-diaphragm. Despite this, no respiratory muscle fatigue and an adequate blood oxygen saturation concentration at room air were noted and the patient was able to tolerate up to 96 hours of pacing before his diaphragm fatigued. The patient was ventilator-free completely at 20 weeks after implantation and a trial of spontaneous respiration without PNS and DP was attempted after patient counseling at 24 weeks after surgery; however, the patient was able to sustain a normal respiration profile only for 5 minutes at the first such attempt and in subsequent trials until the last follow-up visit. At 36 months after surgery, our patient remained reliant on DP with an SCIM III score of 7 points (4 points for respiration and 3 points for bladder management), has not required MV since, is on a capped tracheostomy tube, and is ambulant in a motorized wheelchair. During his rehabilitation, the patient’s pulmonary function improved, with a change in the SCIM III respiration score from 0 to 4 points and without any pulmonary or procedure-related complications. This has enabled the patient to actively undergo a holistic rehabilitation without any episodes of anxiety or depression and with an objective improvement in the quality of life on the World Health Organization’s Quality of Life–BREF (WHOQOL-BREF) questionnaire with high transformed scores domain-wise attained (i.e., 56 points in physical health, 69 points in psychological, 69 points in social relationships, and 100 points in environment) [19].