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Biomedical subjects

A Romaniello

Publications and source records attributed to A Romaniello.

35 records · Page 2Linked to original sources
PubMed2000

Effect of experimental pain from trigeminal muscle and skin on motor cortex excitability in humans.

The pathophysiology of many orofacial pain syndromes is still unclear. We investigated the effect of tonic muscle and skin pain on the excitability of the trigeminal motor pathways using transcranial magnetic stimulation (TMS). Motor evoked potentials (MEPs) were recorded in the masseter surface electromyogram (EMG). Magnetic pulses were delivered with a large coil at intensities 1.1 and 1.5 times the motor threshold, and for each intensity, MEPs were recorded at three different clenching levels: 15, 30 and 45% of maximum voluntary contraction (MVC). Baseline, pain and post-baseline recordings were compared in two sessions. Firstly, muscle pain was induced by infusion of hypertonic saline (5.8%) into the left masseter. Secondly, skin pain was induced by topical application of capsaicin (5%) on the left cheek. Muscle and skin pain did not induce significant effects on the amplitude or latency of the MEPs (ANOVAs: P>0.50). In both sessions, the amplitude of the MEPs increased with the increase of the clenching level and stimulus intensity (P<0.0001; P<0.005) whereas the latency was not significantly changed (P>0.05; P=0.11). Muscle pain was associated with an increase in the pre-stimulus EMG activity on the non-painful side compared with baseline (P<0.01), which could be due to compensatory changes in the activation of the painful muscle. The need for voluntary contraction to evoke MEPs in the masseter muscles and compensatory mechanisms both at the brainstem and cortical level might explain the lack of detectable modulation of MEPs. Nonetheless, the present findings did not support the so-called 'vicious cycle' between pain - central hyperexcitability - muscle hyperactivity.

Adult↗
PubMed2000

Conduction velocity of the human spinothalamic tract as assessed by laser evoked potentials.

To study the conduction velocity of the spinothalamic tract (STT) we delivered CO2 laser pulses, evoking pinprick sensations, to the skin overlying the vertebral spinous processes at different spinal levels from C5 to T10 and recorded evoked potentials (LEPs) in 15 healthy human subjects. These stimuli yielded large-amplitude vertex potentials consisting of a negative wave at a peak latency of about 200 ms followed by a positive wave at a peak latency of about 300 ms. The mean conduction velocity of the STT was 21 m/s, i.e. higher than the reported velocity of the corresponding primary sensory neurons (type II AMH). Because dorsal stimulation readily yields reproducible brain LEPs, we expect this technique to be useful as a diagnostic tool for assessing the level of spinal cord lesions.

Adult↗
PubMed2000

Prepulse inhibition of the blink reflex by laser stimuli in normal humans.

The subcortical integrative effects of laser-induced activation of pain ascending tracts were examined in 11 healthy volunteers, aged 22-52 years. Subjects underwent either CO2 laser stimulation at the dorsum of the hand, electrical stimulation of digital nerves at the 3rd finger, or mechanical taps to the first dorsal interosseous space, preceding a blink reflex elicited by a supraorbital nerve electrical stimulus. The percentage inhibition induced in the R2 response of the blink reflex was similar for the three different stimulus modalities, but occurred at a different time interval. Compared to control trials, the R2 response of the test trials was a mean of 23.1% at the interval of 250 ms with laser stimuli, 17.4% at the interval of 100 ms with electrical stimuli to the 3rd finger, and 20.6% at the interval of 90 ms with a mechanical tap to the 1st interosseous space. Activation of pain receptors induces prepulse inhibition of the blink reflex at a delay corresponding to a slowly conducting pathway. The percentage inhibition is similar to that observed with other somatosensory inputs.

Adult↗
PubMed2000

Topographical distribution of pinprick and warmth thresholds to CO2 laser stimulation on the human skin.

We studied the topographical distribution of laser sensory thresholds on the human hairy skin, using a small laser beam for pinprick and a large beam for warmth sensations. The threshold for pinprick sensation correlated positively with the distance from the brain, suggesting that Adelta nociceptors, the fibers which convey pinprick sensation, are more dense at proximal than at distal body sites. This finding adds information to skin biopsy studies of epidermal free nerve endings which showed a similar gradient, but could not differentiate small myelinated from unmyelinated fiber afferents. Possibly because of a diffuse low density of warmth receptors, laser warmth thresholds showed no trend.

Adult↗
PubMed2000

Shortened cortical silent period in facial muscles of patients with cranial dystonia.

OBJECTIVE: To study the cortical silent period (SP) in the orbicularis oculi and perioral muscles in 23 patients with cranial dystonia and 10 age-matched control subjects. METHODS: High-intensity magnetic stimuli were delivered with a round coil centered at the vertex during a maximal muscle contraction. Electromyographic (EMG) responses were recorded from surface electrodes placed over the orbicularis oculi and perioral muscles. RESULTS: SPs elicited in upper and lower facial muscles had a similar duration. Facial muscle SPs were significantly shorter in patients than in control subjects. Patients with blepharospasm plus oromandibular dystonia had shorter SPs than patients with blepharospasm alone. Although patients' recordings showed reduced voluntary and evoked EMG activity, neither activities correlated with the duration of the SP. CONCLUSIONS: Silent period (SP) shortening depends neither on the level of electromyographic activity nor on segmentary mechanisms. The shortened SP in facial muscles reflects hypoexcitability of cortical inhibitory neurons in cranial dystonia.

Adult↗
PubMed2000

Sensory involvement in spinal-bulbar muscular atrophy (Kennedy's disease).

Spinal-bulbar muscular atrophy (SBMA) is a rare X-linked neuronopathy associated with an abnormal representation of androgen receptors in the nervous system. Standard nerve conduction and histopathological studies have disclosed the involvement of large myelinated sensory fibers in the spinal nerves of SBMA patients. Little is known about the involvement of small sensory neurons and trigeminal nerves. Laser evoked potentials (LEPs) were studied in 6 unrelated patients with SBMA; 5 of these patients also underwent trigeminal reflex recordings, and 3 a sural nerve biopsy. LEPs were markedly abnormal, indicating a dysfunction in pain pathways. Given the sparing of small fibers in the sural nerve specimens, we hypothesize a dysfunction in spinothalamic cells, possibly due to an abnormal representation of the androgen receptors. Except for the jaw-jerk, all the trigeminal reflexes were markedly abnormal. Since the afferents for the jaw-jerk have their cell body within the central nervous system instead of the ganglion, the selective sparing of the jaw-jerk indicates a trigeminal ganglionopathy.

Aged↗
PubMed2000

Modulation of exteroceptive suppression periods in human jaw-closing muscles induced by summation of nociceptive and non-nociceptive inputs.

Convergence of various afferent inputs onto brain-stem neurons may play an important role in the regulation of trigeminal motor function. The present study examined the efficacy of nociceptive and non-nociceptive perioral stimulation for the modulation of the two exteroceptive suppression periods (ES1 and ES2) in human jaw-closing muscles. The inhibitory jaw-reflexes, ES1 (10-15 ms onset) and ES2 (40-50 ms onset), were recorded as the surface electromyogram of masseter and temporalis muscles in 14 healthy subjects. Non-painful electrical stimuli were applied to the right mental nerve while the subject was biting at 50% of the maximal voluntary force. Five conditions were compared: baseline, repetitive tactile stimulation (1 Hz) on the right cheek, topical application of capsaicin (5%) on the right cheek, repetitive tactile stimulation plus capsaicin, and postbaseline. The perceived intensity of the electrical stimuli was evaluated by the subjects on a 0-10 rating scale. Capsaicin alone failed to induce significant changes of ES1 and ES2; tactile stimulation alone induced a significant delay in the onset of ES2 (P < 0.001). During repetitive tactile stimulation plus capsaicin, the duration of ES1 and ES2 was shortened (ES1 and ES2: P < 0.001) and the degree of suppression was reduced (ES1: P < 0.05; ES2: P < 0.005). Perceived intensity of the electrical stimuli was unchanged during the different experimental conditions. The present results suggest that summation of simultaneous nociceptive and non-nociceptive inputs plays an important role in the modulation of the neural pathways involved in the short-latency ES1 and long-latency ES2.

Adult↗
PubMed2000

Trigeminal small-fibre dysfunction in patients with diabetes mellitus: a study with laser evoked potentials and corneal reflex.

OBJECTIVE: To investigate trigeminal small-fibre function in patients with diabetes mellitus. METHODS: In 52 diabetic patients we studied the trigeminal laser evoked potentials after stimulation of the skin bordering the lower lip. In the 21 patients with the severest peripheral nerve damage we also studied the electrically evoked corneal reflex. Both responses are mediated by small myelinated afferents. RESULTS: Laser evoked potentials had a longer mean latency and lower amplitude in diabetic patients than in normal subjects (P<0.005). The abnormality frequency of the laser evoked potentials correlated with the severity of polyneuropathy (P<0.005). In contrast, the corneal reflex was normal. CONCLUSION: Dysfunction of small afferents of the mandibular nerve is frequent in patients with diabetic polyneuropathy. We speculate that the primary cause could be segmental demyelination.

Adult↗
PubMed2000

Dysfunction of small myelinated afferents in diabetic polyneuropathy, as assessed by laser evoked potentials.

OBJECTIVE: To verify whether laser evoked potentials are useful in assessing the function of small afferent fibers and to compare dysfunction of large and small afferent fibers in patients with diabetic polyneuropathy. METHODS: The brain potentials evoked by CO2 laser stimulation of the hand and foot were studied in diabetic patients (n = 45) with various degrees of peripheral nerve damage. Laser evoked potentials (which assess the function of small myelinated afferents) were also compared with ulnar and sural nerve sensory action potentials (which assess the function of large myelinated afferents) by scoring the abnormalities of the two neurophysiological tests with similar criteria. RESULTS: Laser evoked potentials were often absent; the mean latency was normal and mean amplitude decreased, as expected in axonopathies. Although clinical examination showed more frequent impairment of vibratory than pinprick sensation, laser evoked potentials and sensory action potentials yielded similar abnormality scores and showed a strong intra-individual correlation. CONCLUSIONS: Laser evoked potentials, possibly better than standard clinical examination for assessing the abnormalities of small-diameter afferents, indicate that diabetic polyneuropathy induces large- and small-afferent dysfunction in parallel.

Brain↗
PubMed2000

Comparative study on sensory recovery after oral cavity reconstruction by free flaps: preliminary results.

Anatomical restoration was once the only goal of reconstructive surgery, but now it represents only one step in the complete functional recovery process to allow resumption of physiological activity. Soft tissue and nerves play important roles in functional recovery, but the potential of these structures is not yet well known. Rehabilitation after oral cavity reconstruction by free flaps needs an interdisciplinary diagnostic and therapeutic approach, in which neurosensory recovery of transferred tissue is an important aspect. Previous studies have used clinical assessment to evaluate sensory recovery after oral reconstruction with free flaps, but these results have been subjective and not quantifiable. The aim of the present study is to evaluate the sensory recovery using objective and standardized electrophysiological data by recording the masseter inhibitory reflexes (MIR) following mental and lingual electrical stimulation. A group of 14 patients who underwent oral cavity reconstruction by transplantation of either forearm (9) or jejunal (5) noninnervated free flaps were investigated. We found that sensory recovery of fasciocutaneous radial forearm free flaps was better than that of jejunal free flaps. This could represent the starting point for further studies about sensory recovery of reconstructed anatomical structures based on standardized and objective electrophysiological data.

Adult↗
PubMed1999

Assessment of trigeminal small-fiber function: brain and reflex responses evoked by CO2-laser stimulation.

Laser pulses selectively excite mechano-thermal nociceptors and evoke brain potentials that may reveal small-fiber dysfunction. We applied CO2-laser pulses to the perioral and supraorbital regions and recorded the scalp laser-evoked potentials (LEPs) and reflex responses in the orbicularis oculi, masticatory, and neck muscles in 30 controls and 10 patients with facial sensory disturbances. Low-intensity pulses readily evoked scalp potentials consisting of a negative component with a latency of 165 ms followed by a positive component at 250 ms. In vertex recordings, the amplitude of LEPs exceeded 30 microV. Although only high-intensity pulses evoked reflex responses, some subjects showed--even to low-intensity pulses--an orbicularis oculi (blink-like) response that markedly contaminated the scalp recording. Scalp LEPs were abnormal in patients with hypalgesia and normal trigeminal reflexes and normal in patients with normal pain sensitivity and abnormal trigeminal reflexes. Possibly because of the high receptor density in this area and the short conduction distance, laser stimulation of the trigeminal territory yields low-threshold and large LEPs, which are useful for detecting dysfunction in peripheral and central pain pathways.

Adult↗
PubMed1998

Mandibular nerve involvement in diabetic polyneuropathy and chronic inflammatory demyelinating polyneuropathy.

Sensory complaints in the area of the mandible and mouth often escape notice or remain undiagnosed. Using electromyographic recording of the trigeminal reflexes and motor responses, we sought trigeminal dysfunction in 50 patients with peripheral neuropathy, and tried to gain pathophysiological information on the mechanisms provoking trigeminal damage. Trigeminal reflex recordings (early and late blink reflex after supraorbital stimulation, early and late masseter inhibitory reflex after mental stimulation, and jaw jerk) disclosed abnormalities caused by sensory trigeminal neuropathy in 8 out of 15 patients with chronic inflammatory demyelinating polyneuropathy (CIDP), 13 out of 23 patients with severe diabetic polyneuropathy, and in none of 12 patients with mild diabetic polyneuropathy. Six patients had abnormal motor responses in facial or masseter muscles. The response affected most frequently was the masseter early inhibitory reflex (also called first silent period, SP1) after mental nerve stimulation, its latency being strongly delayed. We found these long delays not only in patients with CIDP, but also in diabetic patients with severe polyneuropathy. We conclude that peripheral polyneuropathies often cause subclinical damage to the trigeminal nerve, especially to its mandibular branch. We believe that the nerve fibers running along the alveolar-mandibular pathway are more exposed to damage because of their cramped anatomical route in the mandibular canal and below the internal pterygoid muscle and fascia.

Adolescent↗
PubMed1998

Jaw-opening reflex after CO2 laser stimulation of the perioral region in man.

CO2 laser pulses selectively excite A-delta and C mechano-thermal nociceptors in the superficial layers of the skin. To study the jaw-opening reflex elicited by a purely nociceptive input, we delivered laser pulses to the perioral region in 15 subjects. Sensory threshold was very low (9 mJ/mm2). High-intensity noxious laser pulses (more than 4 x sensory threshold) evoked a single phase of electromyogram suppression (laser silent period, LSP) at an onset latency of 70 ms in the contracted masseter and temporal muscles, bilaterally. Even maximum-intensity laser pulses failed to activate the suprahyoid muscles. The recovery curves to paired laser stimuli showed that at short interstimulus intervals the test LSP was strongly suppressed. At about 380 ms it recovered to 50%, i.e. its recovery curve resembled that of the masseter late silent period after electrical mental nerve stimulation (SP2). In experiments studying the interaction with heterotopic stimuli and non-nociceptive responses, chin-taps or electrical shocks delivered to the supraorbital, infraorbital or mental nerves before laser stimulation strongly suppressed the LSP. A preceding perioral laser pulse strongly suppressed the masseter SP evoked by supraorbital stimulation and the SP2 evoked by mental stimulation, but left SPI unaffected. We conclude that the perioral A-delta fibre input elicits a jaw-opening reflex simply by inhibiting the jaw-closers. The LSP response is mediated by a multisynaptic chain of brainstem interneurons and shares with the masseter SP2 part of the central circuit in the ponto-medullary region. We also propose that a common centre processes the various inputs for jaw opening.

Adult↗
PubMed1997

Cortical mechanisms mediating the inhibitory period after magnetic stimulation of the facial motor area.

We studied the silent period (SP) that interrupts voluntary electromyographic activity (EMG) in facial muscles, after transcranial magnetic stimulation (TMS), in normal subjects. High-intensity magnetic stimulation with a 12-cm round coil centered at the vertex induced a long-lasting SP (215 ms), whereas supramaximal stimulation of the facial nerve only induced a short (< 20 ms) and incomplete EMG suppression, and cutaneous stimuli had no inhibitory effect at all. Cutaneous trigeminal stimulation delivered after TMS evoked blink-like reflexes, showing that facial motoneurons were not inhibited during the SP. Simultaneous recordings from perioral muscles (large cortical representation) and from orbicularis oculi and masseter muscles (small cortical representation) showed SPs of identical duration. Focal stimuli with a figure-of-eight coil showed that positioning of the coil was critical and that the optimal scalp sites for evoking the largest motor potentials and longest SPs coincided. Low-intensity stimulation occasionally elicited short SPs without a preceding motor potential. We conclude that the SP induced in facial muscles by TMS results from the excitation of cortical inhibitory interneurons surrounding the upper motoneurons.

Adult↗
PubMed1997

Excitability of the central masticatory pathways in patients with painful temporomandibular disorders.

Much is unclear about the pathophysiological mechanisms underlying painful temporomandibular disorders. In addition to various other theories, masticatory muscle dysfunction and pain have also been attributed to primary central nervous system hyperactivity. We assessed this possibility in a study using recent neurophysiological techniques. From among outpatients whose diagnosis of temporomandibular disorders had been obtained in stomatognathic facilities, we studied 10 patients with bilateral pain and 15 patients with unilateral pain, in whom electromyographic examination of the trigeminal reflexes disclosed normal findings except for absence or amplitude asymmetry of the jaw jerk. Transcranial magnetic stimulation yielded masseter motor evoked potentials of normal latency and amplitude, but five patients had to exert a near-maximum contraction to obtain their responses. The masseter silent periods elicited by the double-shock technique recovered normally. Because these tests measure the excitability of the masticatory system (including motor cortex, corticobulbar and corticoreticular connections, reticular interneurones and lower motoneurones), the lack of facilitation in these patients' responses excluded central hyperactivity as the primary cause of their masticatory dysfunction and pain.

Adult↗