Hypothermia-Induced Peripheral Polyneuropathy After an Episode of Drowning

Nonfreezing Cold Injury (Trench Foot)

Nonfreezing cold injury (NFCI) is a modern term for trench foot or immersion foot. Moisture is required to produce a NFCI. NFCI seldom, if ever, results in loss of tissue unless there is also pressure necrosis or infection. Much of the published material regarding management of NFCIs has been erroneously borrowed from the literature on warm water immersion injuries. NFCI is a clinical diagnosis. Most patients with NFCI have a history of losing feeling for at least 30 min and having pain or abnormal sensation on rewarming. Limbs with NFCI usually pass through four 'stages.' cold exposure, post-exposure (prehyperaemic), hyperaemic, and posthyperaemic. Limbs with NFCI should be cooled gradually and kept cool. Amitriptyline is likely the most effective medication for pain relief. If prolonged exposure to wet, cold conditions cannot be avoided, the most effective measures to prevent NFCI are to stay active, wear adequate clothing, stay well-nourished, and change into dry socks at least daily.

A 4-year follow-up of non-freezing cold injury with cold allodynia and neuropathy in 26 naval soldiers

Background and aims Non-freezing cold injuries (NFCI), which typically may occur in military personnel, may result from exposure to cold, at temperatures around 0 °C or above, and worsened by wind and moisture. The injury is due to cooling but not freezing of tissue like in frostbite. NFCI may result in in chronic neuropathy and cold hypersensitivity. A recent retrospective study of small-and large fibres has suggested that NFCI results in neuropathic pain due to a sensory neuropathy and question a longitudinal study to verify a possible observation of improvement of NFCI over time. The present study is a 4-year follow-up investigation of large - and small-fibre function in 26 naval cadets and officers who were exposed to cold injury during the same military expedition. Methods The 26 soldiers were investigated clinically (with investigation of motor function, reflexes, sensibility), with nerve conduction studies (NCS) of major nerves in upper- and lower extremity, small fibre testing (QST, measurement of thermal thresholds), measurements of subcutaneous fat tissue and maximal O2 uptake. Investigations found place 2 months following the actual military expedition, with follow-up investigations of affected soldiers at 6-12 months and up to 3-4 years. In order to elucidate possible mechanisms (disinhibition of cold pain by myelinated nerve fibres) of cold allodynia, cold pain thresholds were measured following an ischemic block of conduction of large and small myelinated nerve fibres. Results Of 26 soldiers, 19 complained of numbness in feet and a large majority of 16 of cold hypersensitivity 2 months following injury. There were significant alterations of both large- and small-fibre function, indicating a general large- and small-fibre neuropathy. The most prominent finding was a pronounced cold allodynia, inversely correlated with the amount of subcutaneous fat. During the first year, results of NCS and thermal testing gradually normalized in most. Seven soldiers developed chronic symptoms in the form of cold hypersensitivity and with findings of cold allodynia, which was not further enhanced, but abolished following block of conduction of myelinated nerve fibres. Seven soldiers were free of symptoms from that start of the investigation, probably because they had been more eager to keep their legs moving during the exposure to cold. Conclusions Of a total of 26 soldiers, only seven developed chronic symptoms of cold hypersensitivity, corresponding to the finding of cold allodynia by thermal testing. The cold allodynia may not be explained by disinhibition of cold pain by myelinated fibres as in healthy subjects. A large majority recovered from an initial large-and small fibre neuropathy, demonstrating that recovery from NFCI may occur. Implications Although large-and small fibre neuropathy may be restored following cold injury, there is a risk of a permanent and disabling cold hypersensitivity, corresponding to the findings of cold allodynia. It is of uttermost importance to secure military personnel from the risk of cold injuries. It seems important to avoid immobilisation of extremities during exposure to cold.

Trench Foot or Non-Freezing Cold Injury As a Painful Vaso-Neuropathy: Clinical and Skin Biopsy Assessments

Background

Trench foot, or non-freezing cold injury (NFCI), results from cold exposure of sufficient severity and duration above freezing point, with consequent sensory and vascular abnormalities which may persist for years. Based on observations of Trench foot in World War II, the condition was described as a vaso-neuropathy. While some reports have documented nerve damage after extreme cold exposure, sensory nerve fibres and vasculature have not been assessed with recent techniques in NFCI.

Objective

To assess patients with chronic sensory symptoms following cold exposure, in order to diagnose any underlying small fibre neuropathy, and provide insight into mechanisms of the persistent pain and cold hypersensitivity.

Methods

Thirty soldiers with cold exposure and persistent sensory symptoms (>4 months) were assessed with quantitative sensory testing, nerve conduction studies, and skin biopsies. Immunohistochemistry was used to assess intraepidermal (IENF) and subepidermal (SENF) nerve fibres with a range of markers, including the pan-neuronal marker protein gene product 9.5 (PGP 9.5), regenerating fibres with growth-associated protein 43 (GAP43), and nociceptor fibres with transient receptor potential cation channel subfamily V member 1 (TRPV1), sensory neuron-specific receptor (SNSR), and calcitonin gene-related peptide (CGRP). von Willebrand factor (vWF), endothelial nitric oxide synthase (eNOS), and vascular endothelial growth factor (VEGF) were used for assessing blood vessels, and transient receptor potential cation channel, subfamily A member 1 (TRPA1) and P2X purinoceptor 7 (P2X7) for keratinocytes, which regulate nociceptors via release of nerve growth factor.

Results

Clinical examination showed pinprick sensation was abnormal in the feet of 20 patients (67%), and between 67 and 83% had abnormalities of thermal thresholds to the different modalities. 7 patients (23%) showed reduced sensory action potential amplitude of plantar nerves. 27 patients (90%) had decreased calf skin PGP 9.5 IENF (p < 0.0001), the remaining 3 patients had decreased nerve markers in subepidermis or foot skin. There were marked increases of all vascular markers (for vWF in calf skin, p < 0.0001), and increased sensory or regenerating SENF (for calf skin, GAP43, p = 0.002). TRPA1 (p = 0.0012) and P2X7 (p < 0.0001) were increased in basal keratinocytes.

Conclusion

A range of skin biopsy markers and plantar nerve conduction studies are useful objective assessments for the diagnosis of peripheral neuropathy in NFCI. Our results suggest that an increase in blood vessels following tissue ischaemia/hypoxia could be associated with disproportionate and abnormal nerve fibres (irritable nociceptors), and may lead to NFCI as a “painful vaso-neuropathy.”

Peripheral neuropathy caused by severe hypothermia

OBJECTIVE

To report follow-up data in the evaluation of peripheral neuropathy in a 29-year old female after accidental deep hypothermia (13.7°C) in 1999.

METHODS

Nerve conduction studies (NCS) and electromyography (EMG) were performed 20 days after the accident and again after 5 months and 1, 3, 5 and 11 years. Macro EMG was performed after 3, 5 and 11 years. To evaluate small fiber function, RR-interval, sympathetic skin response, quantitative sensory testing and skin biopsy for quantification of intra-epidermal nerve fiber density were performed in 2009.

RESULTS

In the intensive care unit sensory and motor responses were absent except for the tibial nerves, and EMG showed profuse denervation. Improvement of amplitudes and conduction velocities was seen during the first 5 years. Muscular atrophy of hand muscles persisted. Large fibers were involved more extensively than small fibers.

CONCLUSIONS

A severe axonal sensorimotor polyneuropathy developed in the intensive care unit following severe hypothermia. The mechanism was most likely cold injury to peripheral nerves.

SIGNIFICANCE

The clinical picture and the laboratory findings indicate that even multi-organ dysfunction and, of specific interest in this study, a severe axonal degeneration may come to a good restitution after long time.