The value of comparing mortality of Guillain-Barré syndrome across different regions

OBJECTIVE

To study the clinical profile of Guillain-Barré syndrome (GBS) patients who died in 4 Asian countries in order to understand factors underlying any variation in mortality.

METHODS

Retrospectively reviewed medical records of GBS patients who died in 7 hospitals from 4 Asian countries between 2001 and 2012. Baseline characteristics, timing and causes of death were recorded.

RESULTS

A total of 16 out of 261 GBS patients died. The overall mortality rate was 6%, with a range of 0 to 13%. The leading causes of death were respiratory infections, followed by myocardial infarction. The median age of our patients was 77 years. Half of the patients required mechanical ventilation and almost all had significant concomitant illnesses. A disproportionate number of patients in the Hong Kong cohort died (13%). Patients with advanced age, fewer antecedent respiratory infections and need for mechanical ventilation were at most risk. Most deaths occurred during the plateau phase of GBS and on the general ward after having initially received intensive care.

CONCLUSIONS

There is considerable variability in mortality of GBS among different Asian cohorts. Although the risks factors for mortality were similar to Western cohorts, the timing and site of death differed. This allows specific measures to be implemented to improve GBS care in countries with higher mortality.

Antibodies to single glycolipids and glycolipid complexes in Guillain-Barré syndrome subtypes

OBJECTIVE

To comprehensively investigate the relationship between antibodies to single glycolipids and their complexes and Guillain-Barré syndrome subtypes and clinical features.

METHODS

In acute sera from 199 patients with Guillain-Barré syndrome, immunoglobulin G (IgG) antibodies to glycolipids and ganglioside complexes were tested using ELISA against individual antigens from single glycolipids including gangliosides (LM1, GM1, GM1b, GD1a, GalNAc-GD1a, GD1b, GT1a, GT1b, GQ1b) and a neutral glycolipid, asialo-GM1 (GA1), and antigens from the combination of 2 different glycolipids. Based on serial nerve conduction studies, the electrodiagnoses were as follows: 69 demyelinating subtype, 85 axonal subtypes, and 45 unclassified.

RESULTS

Significant associations were detected between acute motor axonal neuropathy subtype and IgG antibodies to GM1, GalNAc-GD1a, GA1, or LM1/GA1 complex. Reversible conduction failure was significantly associated with IgG antibodies to GM1, GalNAc-GD1a, GD1b, or complex of LM1/GA1. No significant association was demonstrated between acute inflammatory demyelinating polyneuropathy and any of the glycolipids or ganglioside complexes. Anti-ganglioside complex antibodies alone were detected in 7 patients (5 axonal subtype).

CONCLUSIONS

The current study demonstrates that antibodies to single glycolipids and ganglioside complexes are associated with acute motor axonal neuropathy or acute motor conduction block neuropathy but not acute inflammatory demyelinating polyneuropathy.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that antibodies to glycolipids are increased in patients with acute motor axonal neuropathy and acute motor conduction block neuropathy but not acute inflammatory demyelinating polyneuropathy.

[NMDA receptor encephalitis in the course of recurrent CNS demyelinating disorders: a case report]

We present the case of a 31-year-old woman who developed N-methyl-d-aspartate (NMDA) receptor encephalitis during the course of relapsing and remitting multiple brain lesions. The patient developed a tingling sensation in the left upper and lower extremities, and was first admitted to our hospital at age 27. She was tentatively diagnosed with multiple sclerosis on the basis of multiple lesions with Gd-enhancement in the brainstem, and 2 separate clinical relapses by age 28. At age 31, she developed a headache and pyrexia, followed by confusion and abnormal behavior. Her symptoms acutely progressed to stupor, and subsequently, she developed oral dyskinesia and athetosis-like involuntary movement of the left arm. The stupor state continued over 2 months. However, she had completely recovered by 3 months after the onset of psychiatric symptoms. Her serum and CSF samples tested positive for anti-NMDA receptor antibodies, and she was diagnosed with NMDA receptor encephalitis. Her serum was negative for anti-AQP4 antibody, but showed weak positivity for antinuclear antibody. Between ages 32 and 34, she experienced 2 clinical relapses, including right-hand clumsiness, confusion, aphasia, and dysphagia. FLAIR images showed a high-intensity area in the brain stem, thalamus, and subcortical white matter. No tumors were found throughout the course. A clinical entity of NMDA receptor encephalitis can include various neurologic disorders, such as the development of recurrent demyelinating brain lesions. Further investigation is required to clarify the pathophysiological role of anti-NMDA receptor antibody in our patient.

[Neurosarcoidosis presenting with severe hyposmia and polyradiculopathy]

A 50-year-old woman presented with constriction sensation in the lower part of the chest, paresthesia in the right forearm and hypesthesia in the right thigh. One month later, she noticed a loss of sense of smell. The normal findings of the nasal mucosa and the impaired results of standard olfactory acuity test (T&T olfactometry) and intravenous olfactory test (Alinamin test) suggested a lesion proximal to the nasal mucosa. Sensory disturbances in the segmental areas of cervical, thoracic and lumbar regions were clinically and electrophysiologically attributed to polyradiculopathy. MRI of the brain and whole spine revealed no abnormalities. Cerebrospinal fluid examination showed lymphocytic pleocytosis. Sarcoidosis was diagnosed based on the findings including an elevated serum angiotensin-converting enzyme level, bilateral hilar lymphadenopathy on the chest CT and histological evidence of noncaseating granulomas. Methylprednisolone pulse therapy improved the olfactory and sensory disturbances. Neurosarcoidosis should be considered in the differential diagnosis of olfactory impairment.

Isolated shoulder palsy due to cortical infarction: a case report and literature review of clinicoradiological correlations

Clinicoradiological correlations observed in patients with small cortical infarctions have supported somatotopic representation of different parts of body areas in primary motor cortex. However, isolated shoulder weakness because of infarction in precentral gyrus has rarely been described. We report an 80-year-old woman with isolated shoulder palsy because of cortical ischemic infarction in the base of the left precentral gyrus as confirmed by brain magnetic resonance imaging. In our patient, cardiogenic embolism or Trousseau syndrome associated with lung cancer was considered the cause of ischemic infarction. Physicians should consider small cortical infarction, when a patient complains of sudden onset of shoulder weakness without pain. In line with the previous reports, a responsible cortical lesion in our patient corresponded to motor shoulder area in the motor homunculus reported to be located more medially to the hand area.

Optimization of intravenous immunoglobulin in chronic inflammatory demyelinating polyneuropathy evaluated by grip strength measurement

BACKGROUND

Optimal dose and timing of repeated intravenous immunoglobulin therapy (IVIg) for intractable chronic inflammatory demyelinating polyneuropathy (CIDP) patients have not been determined. The aim of this study was to optimize dose and timing of IVIg for CIDP patients who need frequent IVIg using daily grip strength measurement.

METHODS

Repeated IVIg were administered for two intractable CIDP patients. Grip strength was recorded at home every day to access the clinical change in symptoms, and dose and timing of IVIg were optimized based on the results.

RESULTS

The decrement on grip strength was a sensitive indicator of symptom exacerbation. 100 g of IVIg had a limited effect for each patient. In one patient, symptoms maintained after monthly 60 g of IVIg. In another, 100 g of IVIg every 7 weeks resulted in a marked improvement. After receiving 20 g of IVIg weekly, each patient showed further improvement.

CONCLUSION

Optimal dose and timing possibly vary in each individual patient. Dose titration of IVIg is necessary to avoid over- and undertreatment. The daily self-monitoring of grip strength is a helpful tool for clinical assessment in CIDP.

The demyelination neurophysiological criteria can be misleading in Campylobacter jejuni-related Guillain-Barré syndrome

OBJECTIVE

The exclusive association of Campylobacter jejuni infection with the axonal variant of Guillain-Barré syndrome (GBS) is debatable. The current study aims to elucidate the GBS subtypes of patients with an antecedent C. jejuni infection.

METHODS

Nerve conduction study results of 73 patients with GBS were reviewed. Patients were defined as having a recent C. jejuni infection when there was a positive stool culture or serological evidence of C. jejuni in the presence of preceding diarrhea.

RESULTS

A total of 23 patients had evidence of a recent C. jejuni infection. At the early stage, patients were classified as AMAN (n=9; 39%), AIDP (n=3; 13%) or equivocal (n=9) using existing electrophysiological criteria. Prolonged distal latencies and conduction slowing that were seen in 11 patients rapidly normalized within 3 weeks in seven, whereas four had minor abnormalities throughout the course. Subsequently, all patients showed either acute motor axonal neuropathy pattern or reversible conduction failure.

CONCLUSION

Serial neurophysiology suggests that C. jejuni infections are exclusive to axonal GBS.

SIGNIFICANCE

Our findings suggest that AMAN can demonstrate the full complement of demyelinating features at the early stages of disease.

[Reference values for concentric needle single fiber EMG]

Single-fiber electromyography (SFEMG) is one of the most sensitive diagnostic tests of myasthenia gravis. Single-fiber needle electrodes were used originally, however, disposable concentric needle electrodes have been used increasingly in recent years to avoid infection. We therefore undertook a prospective, multicenter study to establish reference values of concentric needle SFEMG in Japanese subjects for both voluntary and stimulated SFEMG and for two commonly examined muscles, the extensor digitorum communis (EDC) and the frontalis (FRO). 69 normal subjects below the age of 60 years were enrolled at six institutes. The cut-off values for mean consecutive difference (MCD) of individual potentials were calculated using+2.5 SD or 95% prediction limit (one-tail) of the upper 10th percentile MCD value for individual subjects. The recommended cut-off values for individual MCD were 56.8 μs for voluntary SFEMG for EDC, 58.8 μs for stimulated SFEMG for EDC, 56.8 μs for voluntary SFEMG for FRO and 51.0 μs for stimulated SFEMG for FRO. This is the first multicenter study reporting reference values for SFEMG using concentric needles.

Recurrent aseptic meningitis in association with Kikuchi-Fujimoto disease: case report and literature review

Background

Kikuchi Fujimoto disease (KFD), or histiocytic necrotising lymphadenitis, is a benign and self-limiting condition characterised by primarily affecting the cervical lymph nodes. Recurrent aseptic meningitis in association with KFD is extremely rare and remains a diagnostic challenge.

Case presentation

We report a 28-year-old man who presented 7 episodes of aseptic meningitis associated with KFD over the course of 7 years. Histopathological findings of enlarged lymph nodes led to the diagnosis of KFD. The patient’s headache and lymphadenopathy spontaneously resolved without any sequelae.

Conclusions

A diagnosis of KFD should be considered when enlarged cervical lymph nodes are observed in patients with recurrent aseptic meningitis. A long-term prognosis remains uncertain, and careful follow-up is preferred.

Non-demyelinating, reversible conduction failure in Fisher syndrome and related disorders

BACKGROUND

IgG anti-GQ1b antibodies are associated with Fisher syndrome (FS), Bickerstaff brainstem encephalitis (BBE), acute ophthalmoparesis and overlap of FS or BBE with Guillain--Barré syndrome (GBS) (FS/GBS or BBE/GBS). It has not been clearly established if the primary pathology of these disorders is demyelinating or axonal in nature. Rapid resolution of conduction slowing or block without signs of demyelination--remyelination has been reported in axonal subtypes of GBS that are associated with IgG anti-GM1 or -GD1a antibodies. We hypothesised that such reversible conduction failure would be also observed in FS and related disorders.

METHODS

Serial nerve conduction studies were prospectively performed in 15 patients with FS and related conditions.

RESULTS

Neither conduction block nor abnormal temporal dispersion was observed in any of the nerves at any point in all the patients. Conduction velocities for none of the nerves were in the demyelinating range. The amplitude of sensory nerve action potential was decreased in three FS, one FS/GBS and two BBE/GBS patients. Compound muscle action potential amplitudes were decreased in the two BBE/GBS patients. These decreases in amplitudes of sensory nerve action potential and compound muscle action potential promptly resolved without significant change in duration on serial studies.

CONCLUSIONS

Reversible conduction failure was seen in six of the 15 patients with FS and related disorders on serial nerve conduction studies. There were no signs of demyelination or remyelination in the 15 patients. The pathology appears to be primarily non-demyelinating. We believe these conditions form a continuous spectrum with axonal GBS.

Guillain-Barré syndrome associated with normal or exaggerated tendon reflexes

Areflexia is part one of the clinical criteria required to make a diagnosis of Guillain-Barré syndrome (GBS). The diagnostic criteria were stringently developed to exclude non-GBS cases but there have been reports of patients with GBS following Campylobacter jejuni enteritis with normal and exaggerated deep tendon reflexes (DTRs). The aim of this study is to expand the existing diagnostic criteria to preserved DTRs. From the cohort of patients referred for anti-ganglioside antibody testing from hospitals throughout Japan, 48 GBS patients presented with preserved DTR at admission. Thirty-two patients had normal or exaggerated DTR throughout the course of illness whereas in 16 patients the DTR became absent or diminished during the course of the illness. IgG antibodies against GM1, GM1b, GD1a, or GalNAc-GD1a were frequently present in either group (84 vs. 94%), suggesting a close relationship between the two groups. We then investigated the clinical and laboratory findings of 213 GBS patients from three hospital cohorts. In 23 patients, eight presented with normal tendon reflexes throughout the clinical course of the illness. Twelve showed hyperreflexia, with at least one of the jerks experienced even at nadir, and exaggerated reflexes returning to normal at recovery. The other three had hyperreflexia throughout the disease course. Compared to 190 GBS patients with reduced or absent DTR, the 23 DTR-preserved patients more frequently presented with pure motor limb weakness (87 vs. 47%, p = 0.00026), could walk 5 m independently at the nadir (70 vs. 33%, p = 0.0012), more frequently had antibodies against GM1, GM1b, GD1a, or GalNAc-GD1a (74 vs. 47%, p = 0.014) and were more commonly diagnosed with acute motor axonal neuropathy (65 vs. 34%, p = 0.0075) than with acute inflammatory demyelinating polyneuropathy (13 vs. 43%, p = 0.0011). This study demonstrated that DTRs could be normal or hyperexcitable during the entire clinical course in approximately 10% of GBS patients. This possibility should be added in the diagnostic criteria for GBS to avoid delays in diagnosis and effective treatment to these patients.

Neuromuscular transmission is not impaired in axonal Guillain--Barré syndrome

BACKGROUND

Previous studies have shown that anti-GQ1b antibodies induce massive neuromuscular blocking. If anti-GM1 and -GD1a antibodies have similar effects on the neuromuscular junction (NMJ) in human limb muscles, this may explain selective motor involvement in axonal Guillain--Barré syndrome (GBS).

METHODS

Axonal-stimulating single-fibre electromyography was performed in the extensor digitorum communis muscle of 23 patients with GBS, including 13 with the axonal form whose sera had a high titre of serum IgG anti-GM1 or -GD1a antibodies.

RESULTS

All patients with axonal or demyelinating GBS showed normal or near-normal jitter, and no blocking.

CONCLUSION

In both axonal and demyelinating GBS, neuromuscular transmission is not impaired. Our results failed to support the hypothesis that anti-GM1 or -GD1a antibody affects the NMJ. In GBS, impulse transmission is presumably impaired in the motor nerve terminal axons proximal to the NMJ.

Conduction block in acute motor axonal neuropathy

Guillain-Barré syndrome is divided into two major subtypes, acute inflammatory demyelinating polyneuropathy and acute motor axonal neuropathy. The characteristic electrophysiological features of acute motor axonal neuropathy are reduced amplitude or absence of distal compound muscle action potentials indicating axonal degeneration. In contrast, autopsy study results show early nodal changes in acute motor axonal neuropathy that may produce motor nerve conduction block. Because the presence of conduction block in acute motor axonal neuropathy has yet to be fully recognized, we reviewed how often conduction block occurred and how frequently it either reversed or was followed by axonal degeneration. Based on Ho's criteria, acute motor axonal neuropathy was electrodiagnosed in 18 patients, and repeated motor nerve conduction studies were carried out on their median and ulnar nerves. Forearm segments of these nerves and the across-elbow segments of the ulnar nerve were examined to evaluate conduction block based on the consensus criteria of the American Association of Electrodiagnostic Medicine. Twelve (67%) of the 18 patients with acute motor axonal neuropathy had definite (n=7) or probable (n=5) conduction blocks. Definite conduction block was detected for one patient (6%) in the forearm segments of both nerves and probable conduction block was detected for five patients (28%). Definite conduction block was present across the elbow segment of the ulnar nerve in seven patients (39%) and probable conduction block in two patients (11%). Conduction block was reversible in seven of 12 patients and was followed by axonal degeneration in six. All conduction blocks had disappeared or begun to resolve within three weeks with no electrophysiological evidence of remyelination. One patient showed both reversible conduction block and conduction block followed by axonal degeneration. Clinical features and anti-ganglioside antibody profiles were similar in the patients with (n=12) and without (n=6) conduction block as well as in those with (n=7) and without (n=5) reversible conduction block, indicating that both conditions form a continuum; a pathophysiological spectrum ranging from reversible conduction failure to axonal degeneration, possibly mediated by antibody attack on gangliosides at the axolemma of the nodes of Ranvier, indicating that reversible conduction block and conduction block followed by axonal degeneration and axonal degeneration without conduction block constitute continuous electrophysiological conditions in acute motor axonal neuropathy.

Neurophysiological evaluation of trigeminal and facial nerves in patients with chronic inflammatory demyelinating polyneuropathy

Cranial neuropathy is clinically uncommon in patients with chronic inflammatory demyelinating polyneuropathy (CIDP), but there is little information on the neurophysiological examination of cranial nerve involvement. To determine the incidence of trigeminal and facial nerve involvement in patients with CIDP, the direct response of the orbicularis oculi muscle to percutaneous electric stimulation of the facial nerve and the blink reflex (induced by stimulation of the supraorbital nerve) were examined in 20 CIDP patients. The latency of the direct response was increased in 12 patients (60%) and an abnormal blink reflex was observed in 17 patients (85%). There was no correlation between electrophysiological findings and the latencies of the direct and R1 responses and disease duration or clinical grade in CIDP patients. Nevertheless, the prevalence of subclinical trigeminal and facial neuropathy is extremely high in patients with CIDP when examined by neurophysiological tests.

[Distal hereditary motor neuropathy type II with mutation in heat shock protein 27 gene. A case report]

A 48-year-old man was admitted to our hospital with a tendency to stumble during walking. The family history indicated that the father was diagnosed with Charcot-Marie-Tooth disease (CMT) at the age of 55 and his younger sister (aunt) had similar symptoms that were considered to reflect autosomal dominant inheritance. Examination showed no pes cavus or inverted champagne-bottle thighs. In addition, the patient walked with foot drop due to weakness and atrophy of the distal parts of the lower extremities. Sensory examination revealed no deficits or abnormalities. Nerve conduction study and needle electromyography indicated pure motor axonal neuropathy. The diagnosis of distal hereditary motor neuropathy (distal HMN) type II was made. Genetic analysis detected mutation in the heat shock protein 27 (HSP27) gene. A recent report indicated that mutations in the HSP27 gene cause both distal hereditary motor neuropathy and CMT2F. In Japan, there are only a few reports of distal hereditary motor neuropathy with mutation in the HSP27 gene. Distal HMN should be considered in the differential diagnosis of patients with CMT like distal amyotrophy.

[Progressive multifocal leukoencephalopathy with idiopathic CD4 positive T-lymphocytepenia mimicking a low grade glioma on proton MR spectroscopy. A case report]

A 61-year-old man with no history of HIV infection developed a subacutely progressive dementia and left hemiparesis. Brain MRI showed a high intensity lesion in the right frontal lobe on T2 weighted image. There was no contrast enhancement after gadolinium-DTPA administration. 1H MRS revealed a marked decrease in the n-acetyl aspartate/creatine ratios and an increase in the choline/creatine ratio. A lactate peak also was present. A low-grade glioma was suspected and he was admitted to our hospital. On examination, there was a mild dementia and left hemiparesis. A peripheral blood count revealed lymphocytopenia (426/mm3) with a CD4/CD8 ratio of 0.28. No evidence of HIV infection, malignancies or collagen disease was found. A brain biopsy revealed no tumor cells but instead demyelinated brain tissue with large nucleated cells. JC virus antigen was detected in the cells of the demyelinated lesions. A diagnosis of PML associated with idiopathic CD4 positive lymphocytopenia was made. There are only a few reports concerning 1H-MRS findings in patients with PML and the present case illustrates the difficulty of making a differential diagnosis between PML and glioma.

[The bilateral long thoracic nerve palsy presenting with "scapula alata", as a result of weight training. A case report]

A 28-year-old male barber with no similar disease in his family admitted to our hospital because of difficulty of raising his arms in March 2003. When he was 18 years old, he broke his left clavicle. He started weight training from January 2003, then he gradually felt difficulty to raise his arms. Physical examination on admission showed weakness and atrophy of both serratus anterior muscles and there was no weakness in the other muscles. Serum CK level was 806 IU/l and CT scan of the upper thoracic levels revealed atrophy of the serratus anterior muscles on the both sides. Needle electromyography showed neurogenic change in the right serratus anterior muscle. Thus the diagnosis of bilateral long thoracic nerve palsy was made. Bilateral scapular winging (scapula alata) is commonly caused by systemic disease, especially muscular dystrophy or spinal muscular atrophy. Bilateral long thoracic nerve palsy by weight training should be known as one of the cause for the "scapula alata".

Axonal Guillain-Barré syndrome associated with axonal Charcot-Marie-Tooth disease

We report the first case of axonal Guillain-Barré syndrome (GBS) associated with axonal Charcot-Marie-Tooth disease (CMT). A 30-year-old Japanese man, who had suffered leg atrophy and foot deformity since childhood, developed acute weakness in his four limbs following an upper respiratory tract infection. Nerve conduction studies showed low compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) amplitudes in all the nerves tested. Serial studies showed a rapid increase in CMAP amplitude, but no significant change in SNAP, which indicates that the acute event selectively involved motor axons and was superimposed on a baseline motor-sensory axonal neuropathy, probably CMT Type 2. Elevated serum IgG antibodies against GM1 and GM1b, an increase in CSF protein, and rapid clinical and electrophysiological recovery after plasma exchange support the diagnosis of a pure motor axonal form of GBS, acute motor axonal neuropathy. The association may be coincidental, but a particular susceptibility to axonal damage of CMT2 cannot be excluded.

Early diagnosis of vertebral dissecting aneurysm: a magnetic resonance angiography study

We report a patient with dissecting aneurysm who presented with a sudden severe headache without any neurological symptoms. Although brain computed tomography (CT) scan and MRI were negative, magnetic resonance angiography (MRA) showed a pseudocavity in a segment of the left vertebral artery. In addition, the dissecting wall of the left vertebral artery was clearly visualized in the original images of MRA. Our findings indicate that brain CT, MRI or cerebral angiography alone are sometimes inadequate for the diagnosis of vertebral dissecting aneurysm, and that MRA and its original images are necessary to establish the correct diagnosis.

13C-UBT using an infrared spectrometer for detection of Helicobacter pylori and for monitoring the effects of lansoprazole

The stable isotope [13C]-labeled urea breath test (13C-UBT) is very useful for detecting Helicobacter pylori. Conventionally, a mass spectrometer is used to measure the presence of 13CO2 in breath. However, this technique is complex and expensive. Therefore, we carried out the 13C-UBT using an easy-to-operate infrared spectrometer, and we studied its usefulness. The 95 subjects included 35 patients with gastric ulcers, 32 with duodenal ulcers, 13 with gastroduodenal ulcers, some patients with nonulcer gastroduodenal disease, and normal controls. The 13C-UBT was negative in normal controls and positive in 86 of 91 (95%) patients with illness. Peaks appeared 15 to 30 min after [13C]urea administration. The 33 patients who were 13C-UBT-positive were then given lansoprazole 30 mg/day and the 13C-UBT was repeated after 8 to 16 weeks. Lansoprazole was found to be effective in patients who exhibited peak 13CO2 values that were at least two-thirds less than the pretreatment values. This effect was seen in 16 patients (48%), 13 of whom (81%) had gastric ulcers. Thirteen of the 17 patients (76%) who exhibited no effect had duodenal ulcers, and there were clear treatment response differences between the two types of ulcers.

[Determination of 13C abundance in trace amounts of plant metabolites by the infrared 13CO2 analyzer]

The infrared 13CO2 analyzer was improved to measure the 13C abundance in the trace amounts of plant metabolites separated by high performance liquid chromatography (HPLC). To improve the sensitivity to 12C, the range of wave number of 2 360 +/- 10 cm-1 was used for 12C determination. Free carbohydrates in corn leaves fed 13CO2 were separated by HPLC and the 13C abundances in sucrose, glucose and fructose were determined by this improved method. The samples containing 10-40 micrograms of carbon could be successfully analysed.