Increased excitability in the primary motor cortex and supplementary motor area in patients with phantom limb pain after upper limb amputation.

Using functional magnetic resonance imaging and single slice FLASH technique, we investigated reorganization of the hand representation of the primary sensorimotor cortex (SMC) in 16 patients with upper extremity amputation. Patients were asked to perform finger tapping with the intact hand, repetitive eye closing and anteflexion of the amputation stump or intact shoulder. Six normal volunteers served as control. In the normal volunteers activations during shoulder anteflexion, finger tapping and eye closure were located within the central sulcus in a medio-lateral fashion. Patients demonstrated invasion of the face or shoulder representation into the hand representation of the amputated limb. Eight phantom limb pain patients showed significantly greater activation in SMC and supplementary motor area (SMA) in contrast to eight patients without phantom limb pain. We conclude, that different parts of the motor system are affected in patients with phantom limb pain--possibly in the sense of an up-regulation of excitability.

Spontaneous oscillations in cerebral blood flow velocity give evidence of different autonomic dysfunctions in various types of headache.

OBJECTIVES: Our objectives were to determine if: (1) patients with migraine have B wave abnormalities in comparison to normal controls and patients with chronic tension headache and (2) patients with chronic tension headache have an imbalance in autonomic activity that is reflected in differences in Mayer wave activity in comparison to normal controls. BACKGROUND: B waves and Mayer waves are spontaneous oscillations in cerebral blood flow velocity with a frequency of 0.5 to 3 or 4 to 7 cycles per minute, respectively, and can be measured by transcranial Doppler sonography. There is experimental evidence that B waves are generated by certain brain stem nuclei which modulate the lumen of the small intracerebral vessels via monoaminergic nerve endings. In contrast, Mayer waves in cerebral blood flow velocity have no central generator but mirror the Mayer waves in arterial blood pressure which represent peripheral autonomic activity. Migraine may be attributed to a neurotransmitter imbalance in brain stem nuclei. Dysfunctions of the peripheral autonomic nervous system are known in patients with chronic tension headache. METHODS: Using bilateral transcranial Doppler monitoring of the middle cerebral artery B waves and Mayer waves were studied in 30 patients with migraine without aura, 28 subjects with tension-type headache, and 30 normal controls. Coefficient of variation as a quantitative parameter for amplitude of waves and the mean frequency were calculated from the envelope curves of the Doppler spectra. RESULTS: The coefficient of variation of B waves was higher in migrainous patients compared with patients with tension-type headache and normal controls (P<.05), indicating an increase in activity of brain stem nuclei in migraine only. Patients with chronic tension headaches had lower values for Mayer wave activity in comparison with normal controls (P<.05), a sign of an impairment of sympathetic activity. CONCLUSIONS: Our data support the dysfunction of the brain stem monoaminergic/serotonergic system in migraine. In contrast, patients with chronic tension headache have an autonomic dysfunction of peripheral origin presenting as a decrease of sympathetic activity.

Abnormal motor cortex organization contralateral to early upper limb amputation in humans.

We performed both a functional magnetic resonance imaging (fMRI) study using single slice FLASH technique and an investigation with transcranial magnetic stimulation (TMS) in a 21-year-old patient. He had suffered a left upper extremity amputation at age 7. Anteflexion of the amputation stump produced an unusual, broad activation contralateral to the movement. TMS revealed an enlarged cortical motor output area of the deltoid muscle at the amputation stump. Application of paired magnetic stimulation demonstrated decreased intracortical inhibition (ICI). A T1-weighted image indicated a lack of the characteristic shape of the central sulcus contralateral to the amputation. In addition to previous functional studies, these new structural data suggest that maturation of the central sulcus develops in response to daily practice of the contralateral hand, possibly until adolescence.

Pneumosinus dilatans after prolonged cerebrospinal fluid shunting in young adults with cerebral hemiatrophy. A report of two cases and review of the literature.

Pneumosinus dilatans is a generalized or partial enlargement of the paranasal sinuses containing only air. Pneumosinus dilatans occurs as an idiopathic disorder as well as in association with other disorders, including cerebral hemiatrophy. We report two cases of patients with congenital cerebral hemiatrophy who developed juvenile pneumosinus dilatans of the frontal, ethmoidal, and sphenoidal sinus. The hydrocephalus of both patients was treated by prolonged cerebrospinal fluid shunting. The development of hyperpneumatization of the paranasal sinuses was proved by plain radiographs and CT. Previous reports of pneumosinus dilatans are reviewed, and the effect of prolonged cerebrospinal fluid shunting in our cases is discussed. Cerebrospinal fluid shunting during the period of physiological pneumatization of paranasal sinuses might have increased hyperpneumatization.

Contributions of inhibitory mechanisms to the shift responses of X and Y cells in the cat lateral geniculate nucleus.

1. Adult cats were anaesthetized with a mixture of halothane, nitrous oxide and oxygen to record from single neurones of the dorsal lateral geniculate nucleus (d.l.g.n.) with five-barrel glass micro-electrodes. Periphery effects (shift effects) were elicited by large-field phase-reversing gratings presented in the visual field outside the conventional receptive field area. 2. A range of transient excitatory responses was found in X and Y cells. Y cells had phasic shift effects with significantly higher amplitudes and shorter durations (mean 52 impulses/s, 135 ms) than those observed in the tonic shift effects of X cells (mean 24 impulses/s, 169 ms). All Y cells and most X cells responded to stimulation of remote retinal regions. About 7% of the X cells displayed no shift effect. 3. Micro-ionophoresis of the gamma-aminobutyric acid (GABA) antagonist bicuculline, acetylcholine (ACh) and L-glutamate specifically influenced the shift effects of X and Y cells. 4. During continuous application of the GABA antagonist bicuculline the differences in maximal response rates and amplitudes of X and Y cells were eliminated. The maintained activity raised predominantly in X cells and the early peak rates increased more in X- than in Y-cell shift effects, leading to equal average peak rates of 100 and response amplitudes of about 85 impulses/s in both cell classes. The characteristic time courses of X- and Y-cell responses were not affected. 5. Micro-ionophoretic application of ACh caused a combination of excitatory and disinhibitory effects. Maintained activity as well as early parts of stimulus-evoked responses were similarly raised in X and Y cells. In addition, the Y-cell shift effects became less phasic by elevation of the late response part. Sodium pentobarbitone, used to block ACh excitation, suppressed the ACh-induced effects in the early phase of the X- and Y-cell shift effects and the increase of maintained activity in Y-cells, while the effect on the late part of Y-cell responses persisted. Elevation of background activity partially remained in X cells, and the X-cell responses became tonically prolonged at the same time. 6. L-Glutamate increased the activity of X and Y cells without changing the characteristic shift-effect properties of both cell classes. 7. It is concluded that different short- and long-lasting inhibitory mechanisms shape the responses of d.l.g.n. neurones to stimulation outside the conventional receptive field.(ABSTRACT TRUNCATED AT 400 WORDS)

Excitatory and differential disinhibitory actions of acetylcholine in the lateral geniculate nucleus of the cat.

Single neurones were recorded in the dorsal lateral geniculate nucleus (d.l.g.n.) of adult cats anaesthetized with a mixture of halothane, nitrous oxide and oxygen. The multibarrel-glass micro-electrodes were filled with sodium acetate, L-glutamate, acetylcholine (ACh), gamma-aminobutyric acid (GABA) and bicuculline. In normally innervated, spontaneously active d.l.g.n. cells, ACh and L-glutamate elicited increased firing rates. After elimination of the excitatory input from the retina by retinal photocoagulation, the effects of ACh and L-glutamate were similar. This proves that both drugs have direct excitatory effects on d.l.g.n. cells and that disinhibition is not the most prominent influence of ACh in the d.l.g.n. The excitatory action of ACh on relay cells in the d.l.g.n. was strongly influenced by barbiturates. Sub-narcotic levels of sodium pentobarbitone completely abolished the excitation by ACh while the response to L-glutamate remained unchanged. Excitation, centre-surround antagonism and periphery effects were elicited by spots of light and by large field phase-reversing gratings with and without central sparing of the receptive field area. Binocular inhibition was elicited with the phase-reversing grating presented to the non-dominant eye. After localized destruction of the retinal receptive field area, retinogeniculate excitation ceased and an isolated lateral inhibition was observed in the acutely deafferented d.l.g.n. cells. The time course and strength of this inhibition was disclosed by raising the background discharge with microiontophoretically applied L-glutamate. With increasing size of retinal lesions the strength of isolated lateral inhibition decreased exponentially. A maximal intrageniculate range of more than 1000 microns was derived from computations of the lateral extent of deafferentation in the d.l.g.n. The inhibition acted beyond the classic surround inhibition of d.l.g.n. cells and thus was named long-range lateral inhibition. Microiontophoretically applied GABA elicits a strong inhibitory effect at the d.l.g.n. cells which is antagonized by bicuculline. Centre-surround antagonism, binocular inhibition and long-range inhibition were blocked by bicuculline and thus proven to be GABAergic. Each class of inhibition was differentially influenced by microiontophoretically applied ACh. Long-range inhibition was disinhibited, centre-surround antagonism was enhanced, and binocular inhibition was not significantly changed. In contrast to ACh excitation, the disinhibitory action of ACh was not suppressed by pentobarbitone.(ABSTRACT TRUNCATED AT 400 WORDS)