Conduction block and impaired axonal function in tick paralysis

Comprehensive analysis of the global impact and distribution of tick paralysis, a deadly neurological yet fully reversible condition

SUMMARYTick paralysis is a potentially fatal condition caused by neurotoxins secreted by the salivary glands of certain ticks. Documented cases have been reported worldwide, predominantly in the United States, Canada, and Australia, with additional reports from Europe and Africa. This condition also affects animals, leading to significant economic losses and adverse impacts on animal health and welfare. To date, 75 tick species, mostly hard ticks, have been identified as capable of causing this life-threatening condition. Due to symptom overlap with other conditions, accurate diagnosis of tick paralysis is crucial to avoid misdiagnosis, which could result in adverse patient outcomes. This review provides a comprehensive analysis of the current literature on tick paralysis, including the implicated tick species, global distribution, tick toxins, molecular pathogenesis, clinical manifestations, diagnosis, treatment, control, and prevention. Enhancing awareness among medical and veterinary professionals is critical for improving the management of tick paralysis and its health impacts on both humans and animals.

Nodal conduction block: A unifying concept

A newly introduced term, "axonal conduction block," brought a confusion in the electrodiagnostic diagnosis of Guillain-Barrè syndrome (GBS). I am proposing the term "nodal conduction block" for "axonal conduction block." This unifying concept of nodal conduction block will accommodate both the traditional concept of demyelination as well as the new concept of nodopathy in the "axonal form of GBS,", making the practice of electrodiagnosis much easier.

Putative Otobius megnini-associated clinical signs in horses in South Africa (2012-2018)

Otobius megnini has been associated with certain clinical conditions in horses in both California and Mexico. A number of cases similar to those described previously have been identified by the author in South Africa. This case report summarises these cases to demonstrate that the clinical condition occurs readily in South Africa and may be increasing in occurrence. The disease has minimal coverage in the literature making it more likely that a veterinarian, unfamiliar with the disease, will miss the diagnosis. The author would like to make veterinarians aware of this as a potential differential diagnosis. This study is a retrospective review of clinical data. Clinical records of patients with similar clinical signs and treatment were reviewed and grouped together as relevant cases for this case report. Ten cases of O. megnini associated neuromuscular dysfunction are reported, suggesting a link between the occurrence of the tick and the clinical condition. Clinical signs include third eyelid prolapse, localised muscle fasciculations, elevated heart rate and limb stamping. Serum chemistry changes commonly show increased aspartate aminotransferase and creatine kinase enzymes activities. The occurrence of the ticks within South Africa and the increasing number of cases presented demonstrate the need for more investigation into the pathophysiology of this condition.

A Case of Tick-Borne Paralysis in a Traveling Patient

Background

Tick paralysis is a neurotoxic tick-borne illness that causes ascending paralysis and may lead to respiratory failure. Patients often undergo extensive testing and prolonged hospitalization before the proper diagnosis is reached.

Case Presentation

An 88-year-old man with dementia and dyslipidemia presented with new onset gait instability and was admitted for suspected cerebellar stroke. Exam was significant for the inability to perform tandem gait. Investigations included comprehensive metabolic panel, complete blood count, and noncontrast CT scan; none of them found any evidence of acute pathology. Two days into admission, a tick with surrounding erythema was found on the patient's left lateral chest during bathing. Dramatic improvement in truncal ataxia was noted following tick extraction.

Discussion

Clinical suspicion of tick paralysis is often low due to the rarity of the condition. Although it is imperative to rule out acute cerebral or cerebellar pathology, a thorough skin examination should be performed on admission in any patient with new onset ataxia and ascending paralysis. This can lead to early diagnosis, conservation of resources, and the avoidance of subjecting patients to invasive testing.

Electrodiagnostic Abnormalities in Tick Paralysis: A Case Report and Review of Literature

OBJECTIVE

To study the electrodiagnostic abnormalities in tick paralysis.

METHODS

A 7-year-old girl with acute onset proximal muscle weakness and an engorged dog tick attached to her scalp was evaluated.

RESULTS

The routine motor nerve conduction study showed normal compound muscle action potential amplitude. The stimulated jitter analysis of the orbicularis oculi muscle showed normal jitter with no blocking. The quantitative electromyography of the proximal muscles showed decreased mean duration of the motor unit potentials.

CONCLUSION

We propose toxin-mediated direct skeletal muscle involvement as one of the reasons for muscle weakness in tick paralysis.

A Comparative Meta-Analysis of Tick Paralysis in the United States and Australia

CONTEXT

Tick paralysis is a neurotoxic envenoming that mimics polio and primarily afflicts children, especially in hyperendemic regions of the Western United States of America (US) and Eastern Australia.

OBJECTIVE

To compare the epidemiology, clinical and electrodiagnostic manifestations, and outcomes of tick paralysis in the US versus Australia.

METHODS

A comparative meta-analysis of the scientific literature was conducted using Internet search engines to identify confirmed cases of tick paralysis in the US and Australia. Continuous variables including age, time to tick removal, and duration of paralysis were analyzed for statistically significant differences by unpaired t-tests; and categorical variables including gender, regional distribution, tick vector, tick attachment site, and misdiagnosis were compared for statistically significant differences by chi-square or Fisher exact tests.

RESULTS

Tick paralysis following ixodid tick bites occurred seasonally and sporadically in individuals and in more clusters of children than in adults of both sexes in urban and rural locations in North America and Australia. The case fatality rate for tick paralysis was low, and the proportion of misdiagnoses of tick paralysis as Guillain-Barré syndrome (GBS) was greater in the US than in Australia. Although electrodiagnostic manifestations were similar, the neurotoxidromes differed significantly with prolonged weakness and even residual neuromuscular paralysis following tick removal in Australian cases compared with US cases.

DISCUSSION

Tick paralysis was a potentially lethal envenoming that occurred in children and adults in a seasonally and regionally predictable fashion. Tick paralysis was increasingly misdiagnosed as GBS during more recent reporting periods in the US. Such misdiagnoses often directed unnecessary therapies including central venous plasmapheresis with intravenous immunoglobulin G that delayed correct diagnosis and tick removal.

CONCLUSION

Tick paralysis should be added to and quickly excluded from the differential diagnoses of acute ataxia with ascending flaccid paralysis, especially in children living in tick paralysis-endemic regions worldwide.

Suspected tick paralysis (Ixodes holocyclus) in a Miniature Horse

A 9-year-old Miniature Horse gelding infested with ticks (Ixodes holocyclus) was presented with flaccid motor paralysis causing recumbency. Neurological examination and other diagnostic tests did not identify an alternative aetiology, leading to a presumptive diagnosis of tick paralysis. The gelding was treated with tick antiserum and intensive supportive care. He made a gradual recovery over the 48 h following presentation and was discharged without further complications. This case report describes in detail the clinical signs and successful treatment of a Miniature Horse with flaccid paralysis caused by suspected envenomation by Ixodes holocyclus.

Tick paralysis caused by Amblyomma maculatum on the Mexican Pacific Coast

Tick paralysis is a rare entity in which it is necessary to identify the cause and remove the arthropod to have a rapid remission of symptoms. In the absence of an early diagnosis, the outcome can be fatal, as toxins are released from the tick's saliva as it feeds. To the best of the authors' knowledge, this is the first clinical report of the disease in Mexico and Latin America. A 22-year-old man from a rural area, who was in contact with cattle, developed ascending flaccid paralysis secondary to Amblyomma maculatum tick toxin. He presented flaccid paraplegia and arreflexia that progressed until causing dyspnea. The clinical symptoms subsided 48 h after the ticks spontaneously detached. The ticks were discovered by nursing personnel while the patient was being transferred to a regional hospital with the diagnosis of Guillain-Barré syndrome. The patient was asymptomatic on discharge from hospital and showed no further motor deterioration at a 1-month follow-up.

[Brachial plexus sleep palsy]

INTRODUCTION

Brachial plexus is rarely involved in "Saturday night palsy".

CASE REPORT

A young man was admitted for numbness and weakness of his right upper limb after awaking from sleep. Neurophysiological studies, consistent with brachial plexopathy, revealed presence of proximal conduction blocks. Patient presented spontaneous clinical and neurophysiological improvement.

DISCUSSION

Diagnosis of compressive brachial plexopathy needs to eliminate other causes of neuropathy with conduction block.

Utilizing natural activity to dissect the pathophysiology of acute oxaliplatin-induced neuropathy

Oxaliplatin is first-line chemotherapy for colorectal cancer, but produces dose-limiting neurotoxicity. Acute neurotoxicity following infusion produces symptoms including cold-triggered fasciculations and cramps, with subsequent chronic neuropathy developing at higher cumulative doses. Axonal excitability studies were undertaken in 15 oxaliplatin-treated patients before and immediately after oxaliplatin infusion to determine whether the mechanisms underlying acute neurotoxicity altered resting membrane potential or Na(+)/K(+) pump function. Excitability properties were assessed before and after maximal voluntary contraction (MVC) of the abductor pollicis brevis. Following oxaliplatin infusion, abnormalities developed in the recovery cycle with refractoriness markedly increased. Following activity, changes developed consistent with axonal hyperpolarization, with proportional changes pre- and post-oxaliplatin in normalized threshold. However, recovery cycle parameters following activity were significantly and disproportionally enhanced post-oxaliplatin, with partial normalization of the recovery cycle curve post-activity. Patients with the most abnormal change in the recovery cycle after infusion demonstrated the greatest changes post-contraction. Prominent abnormalities developed in Na(+) channel-associated parameters in response to natural activity, without significant alteration in axonal membrane potential or Na(+)/K(+) pump function. Findings from the present series suggest that oxaliplatin affects nerve excitability through voltage-dependent mechanisms, with specific effects mediated through axonal Na(+) channel inactivation.

Tick paralysis

OPINION STATEMENT

Tick paralysis is a toxin-mediated cause of acute flaccid paralysis. Most practitioners will go through their entire career without ever encountering a case. An important veterinary disease, tick paralysis is rare in humans. Although it has certain geographical proclivities, it exists worldwide. Although it tends to occur in young girls, it can occur in any age group. Due to its rarity, doctors often forget to consider tick paralysis in the differential diagnosis of the weak patient. Therefore it is perhaps not surprising that the literature is full of cases in which a mother stroking her child's head or an alert nurse bathing her patient made the diagnosis serendipitously.Physicians should consider tick paralysis in any patient with an acute flaccid paralysis. As a general rule, aimed more towards patient safety than the likelihood of making a correct diagnosis, never definitively diagnose Guillain-Barré syndrome without first searching the entire body for a tick. The treatment of tick paralysis is among the simplest and most gratifying in all of medicine. Tick removal results in rapid improvement of all symptoms. Some patients may require mechanical ventilation and support in an intensive care unit as the toxin clears. Since tick paralysis is toxin-mediated and not caused by an infectious agent, antimicrobials are not indicated. Finally, prevention of tick paralysis, as with most tick-borne diseases, involves changing behavior to avoid tick exposure and performing frequent tick checks to remove them if they have already attached.

Oxaliplatin-induced neurotoxicity: changes in axonal excitability precede development of neuropathy

Administration of oxaliplatin, a platinum-based chemotherapy used extensively in the treatment of colorectal cancer, is complicated by prominent dose-limiting neurotoxicity. Acute neurotoxicity develops following oxaliplatin infusion and resolves within days, while chronic neuropathy develops progressively with higher cumulative doses. To investigate the pathophysiology of oxaliplatin-induced neurotoxicity and neuropathy, clinical grading scales, nerve conduction studies and a total of 905 axonal excitability studies were undertaken in a cohort of 58 consecutive oxaliplatin-treated patients. Acutely following individual oxaliplatin infusions, significant changes were evident in both sensory and motor axons in recovery cycle parameters (P < 0.05), consistent with the development of a functional channelopathy of axonal sodium channels. Longitudinally across treatment (cumulative oxaliplatin dose 776 +/- 46 mg/m(2)), progressive abnormalities developed in sensory axons (refractoriness P < or = 0.001; superexcitability P < 0.001; hyperpolarizing threshold electrotonus 90-100 ms P < or = 0.001), while motor axonal excitability remained unchanged (P > 0.05), consistent with the purely sensory symptoms of chronic oxaliplatin-induced neuropathy. Sensory abnormalities occurred prior to significant reduction in compound sensory amplitude and the development of neuropathy (P < 0.01). Sensory excitability abnormalities that developed during early treatment cycles (cumulative dose 294 +/- 16 mg/m(2) oxaliplatin; P < 0.05) were able to predict final clinical outcome on an individual patient basis in 80% of patients. As such, sensory axonal excitability techniques may provide a means to identify pre-clinical oxaliplatin-induced nerve dysfunction prior to the onset of chronic neuropathy. Furthermore, patients with severe neurotoxicity at treatment completion demonstrated greater excitability changes (P < 0.05) than those left with mild or moderate neurotoxicity, suggesting that assessment of sensory excitability parameters may provide a sensitive biomarker of severity for oxaliplatin-induced neurotoxicity.