Contribution of the pudendal nerve to sensation of the distal rectum

Background

Anal and rectal sensory mechanisms and pudendal nerve function are important in the control of faecal continence. The contribution of the pudendal nerve to sensation of the distal rectum was investigated.

Methods

Heat thresholds in the anal canal, distal and mid rectum were measured using a specially designed thermoprobe. Rectal sensory threshold volumes were measured using the balloon distension method. Needle electrodes were inserted into the external anal sphincter. Pudendal nerve block was performed through a perineal approach, and completeness assessed by loss of electromyographic activity. Heat and rectal volume thresholds were measured again following unilateral and bilateral pudendal nerve block.

Results

The technique was successful in four of six volunteers. Bilateral pudendal nerve block produced complete anaesthesia to heat in the anal canal (P = 0·029), but had no effect on heat thresholds in the distal or mid rectum. Rectal sensory threshold volumes were also unaffected by pudendal nerve anaesthesia.

Conclusion

Anal canal sensation is subserved by the pudendal nerve, but this nerve is not essential to nociceptive sensory mechanisms in the distal or mid rectum. The transition between visceral control mechanisms in the lower rectum and somatic mechanisms in the anal canal may have functional importance in the initiation of defaecation and the maintenance of continence.

The anal reflex elicited by cough and sniff: validation of a neglected clinical sign

BACKGROUND

It is unclear whether contraction of the external anal sphincter (EAS) following a voluntary cough is an integral component of the cough response itself, or a reflex response to the abdominal and pelvic floor dynamics induced by the cough. Clinical experience suggests a reflex origin for this response.

OBJECTIVE

To compare motor latencies for intercostal, abdominal, and EAS muscle contraction after transcranial magnetic stimulation with those following voluntary coughing and sniffing.

METHODS

A needle electrode inserted into the EAS measured responses, which were confirmed by tonic electromyographic recording. Direct motor latencies from the cerebral cortex to the intercostal, rectus abdominis and EAS muscles were obtained using transcranial magnetic stimulation. Sniff and cough induced responses were also recorded in these muscles.

RESULTS

The results suggest that EAS responses following a voluntary cough or sniff represent a polysynaptic reflex.

CONCLUSIONS

As the cough induced anal reflex response is consistent and easily elicited, its use in clinical neurological examination is appropriate.

Acral paresthesias in the Andes and neurology at sea level

BACKGROUND

Thirty-nine percent of permanent altitude dwellers in the Andes experience acral paresthesias.

METHODS

Clinical examinations, sural nerve biopsies, and electrodiagnostic studies on peripheral nerves were performed on 15 men. Ten Cerro de Pasco (CP) natives living at 4,338 meters were biopsied. Three of these subjects had no burning feet/burning hands (BF/BH); three had BF/BH; and four had chronic mountain sickness (CMS), a maladaptation syndrome resulting from living in the Andes, all with BF/BH. Three patients with CMS were biopsied in Lima within hours after leaving CP. Two normal Lima natives were biopsied in Lima. Symptom scores for BF/BH and CMS score ratings were used. The nerves were assayed for Na+, K+ adenosine triphosphatase (ATPase), cytochrome oxidase (CO), substance P (SP), and endothelin (ET).

RESULTS

Low ATPase was inversely related to symptom scores and CMS scores (p < 0.001). Patients with CMS biopsied in normoxia (Lima) had ATPase levels similar to those of controls. Nerve motor conduction velocities and sensory action potentials were normal. CO was inversely related to age (p < 0.03) and no relation of SP to any variable was found. ET levels were lower in sea level natives (p = 0.04).

CONCLUSIONS

Acral paresthesias are associated with low ATPase in peripheral nerves. Lower ET levels of sea level natives likely reflect lowered release from vasa nervorum.

The clinical and laboratory features of chronic sensory ataxic neuropathy with anti-disialosyl IgM antibodies

The clinical and laboratory phenotype of a paraproteinaemic neuropathy syndrome termed chronic sensory ataxic neuropathy with anti-disialosyl IgM antibodies is described in a series of 18 cases. Previous single case reports have outlined some features of this syndrome. All 18 cases were defined by the presence of serum IgM antibodies which react principally with NeuAc (alpha2-8)NeuAc(alpha2-3)Gal-configured disialosyl epitopes common to many gangliosides including GDlb, GD3, GTlb and GQlb. In 17 out of 18 cases, the serum contained benign IgM paraproteins, and in four of these cases at least two IgM paraproteins were present. The IgM antibodies were also cold agglutinins in 50% of cases. The clinical picture comprised a chronic neuropathy with marked sensory ataxia and areflexia, and with relatively preserved motor function in the limbs. In addition, 16 out of 18 cases had motor weakness affecting oculomotor and bulbar muscles as fixed or as relapsing-remitting features. When present in their entirety, these clinical features have been described previously under the acronym CANOMAD: chronic ataxic neuropathy, ophthalmoplegia, IgM paraprotein, cold agglutinins and disialosyl antibodies. This distribution of clinical features is reminiscent of Miller Fisher syndrome, in which acute-phase anti-disialylated ganglioside IgG antibodies are found. Clinical electrophysiology and nerve biopsy show both demyelinating and axonal features. A partial response to intravenous immunoglobulin and other treatments is reported in some cases.

Induced myelination and demyelination in a conditional mouse model of Charcot-Marie-Tooth disease type 1A

Charcot-Marie-Tooth disease type 1A, a hereditary demyelinating neuropathy, is usually caused by overexpression of peripheral myelin protein 22 (PMP22) due to a genomic duplication. We have generated a transgenic mouse model in which mouse pmp22 overexpression can be regulated. In this mouse model, overexpression of pmp22 occurs specifically in Schwann cells of the peripheral nerve and is switched off when the mice are fed tetracycline. Overexpression of pmp22 throughout life (in the absence of tetracycline) causes demyelination. In contrast, myelination is nearly normal when pmp22 overexpression is switched off throughout life by feeding the mice tetracycline. When overexpression of pmp22 is switched off in adult mice, correction begins within 1 week and myelination is well advanced by 3 months (although the myelin sheaths are still thinner than normal), indicating that the Schwann cells are poised to start myelination. Upregulation of the gene in adult mice (which had previously had normal pmp22 expression) is followed by active demyelination within 1 week, which had plateaued by 8 weeks. This indicates that Schwann cells with mature myelin are sensitive to increased amounts of pmp22 such that they rapidly demyelinate. Thus, demyelination can largely be corrected within a few months, but the correction will be sensitive to subsequent upregulation of pmp22.

Long-term clinical and neurophysiological follow-up of patients with peripheral, neuropathy associated with benign monoclonal gammopathy

The incidence of hematological malignancy in patients with monoclonal gammopathy of undetermined significance (MGUS) has been assessed as 17% to 25%. To ascertain whether this is true of neuropathy associated with MGUS, a long-term (5-42 years) retrospective clinical and neurophysiological follow-up was conducted in 50 cases (immunoglobulin M [IgM], n = 38; IgG, n = 11; IgA, n = 1). Only three patients developed hematological malignancy. Of 25 survivors with IgM paraproteinemia, 7 had myelin-associated glycoprotein antibodies with typical clinical features. Evoked distal muscle amplitudes were significantly smaller than for the other paraprotein classes. Preferential distal demyelination manifested by relative prolongation of distal motor latency was not apparent in the cases of long duration. Two patients with IgM antidisialosyl antibodies and cold agglutinating activity had a large fiber neuropathy with intermittent oculofacial involvement. Both responded to intravenous immunoglobulin. Findings in the remaining patients were varied. Recognition of IgM subgroups is important both for prognosis and possible response to treatment.

Medial (cutaneous) branch of deep common peroneal nerve: recording technique and a case report

An isolated lesion of the medial branch of the deep common peroneal nerve is rare and so far there do not appear to have been any reports of a recording method or normative data for this sensory action potential (SAP). Just such a case is described along with an appropriate recording technique. Control data were subsequently obtained from 50 normal volunteers.

Posterior Paroxysmal Discharge: An Aid to Early Diagnosis in Lafora Disease

Lafora body disease is a rare neurometabolic disorder of autosomal recessive inheritance. Symptoms begin in the second decade with progressive myoclonic epilepsy and survival is unusual beyond the age of 30. We report an electroencephalographic study in four cases of histologically proven Lafora body disease. Posterior epileptiform discharges were found even in the early stages of the disease and may assist in early diagnosis.

Posterior paroxysmal discharge: an aid to early diagnosis in Lafora disease

Lafora body disease is a rare neurometabolic disorder of autosomal recessive inheritance. Symptoms begin in the second decade with progressive myoclonic epilepsy and survival is unusual beyond the age of 30. We report an electroencephalographic study in four cases of histologically proven Lafora body disease. Posterior epileptiform discharges were found even in the early stages of the disease and may assist in early diagnosis.

Neurological complications following liver transplantation

17 (33%) of 52 patients who underwent 56 consecutive orthotopic liver transplants had serious neurological complications postoperatively. The commonest complication was fits, which occurred in 13 (25%) patients. 50% of patients had their onset of fits within the first week. In 3 patients the fits were associated with postoperative metabolic encephalopathy and fatal progressive neurological deterioration. In some patients the evidence implicating cyclosporin in the development of fits is strong. In others factors such as electrolyte disturbances, steroid treatment for graft rejection, and cerebral infarction may have contributed to the development of the fits. Phenytoin controlled the fits in 10 out of 13 patients. Other neurological complications included 1 case of central pontine myelinolysis, 1 of cerebral abscess, and 4 of non-encephalopathic psychosis.