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The CSF flows in the aqueduct and at the foramen magnum were examined in 5 patients with communicating hydrocephalus (HC) and in 10 with benign intracranial hypertension (BIH) as well as in 5 healthy volunteers. As compared to normal individuals, the aqueductal flow in HC was about 10 times larger and the cervical flow was half as large. In BIH the CSF flows were not different from those of normal volunteers. The decreased arterial expansion as reflected in the reduced cervical flow in HC may be due to pathologic changes in the arteries and paravascular spaces. The large aqueductal flow in HC reflects a large brain expansion, causing increased transcerebral mantle pressure gradient and ventricular dilatation. In BIH there is a normal brain expansion (aqueductal flow) and consequently no ventricular dilatation. It is argued that BIH be caused by an obstruction on the venous side, as opposed to the vascular alterations in HC, which are on the arterial side.

The CSF flows in the aqueduct and at the foramen magnum were examined in 5 patients with communicating hydrocephalus (HC) and in 10 with benign intracranial hypertension (BIH) as well as in 5 healthy volunteers. As compared to normal individuals, the aqueductal flow in HC was about 10 times larger and the cervical flow was half as large. In BIH the CSF flows were not different from those of normal volunteers. The decreased arterial expansion as reflected in the reduced cervical flow in HC may be due to pathologic changes in the arteries and paravascular spaces. The large aqueductal flow in HC reflects a large brain expansion, causing increased transcerebral mantle pressure gradient and ventricular dilatation. In BIH there is a normal brain expansion (aqueductal flow) and consequently no ventricular dilatation. It is argued that BIH be caused by an obstruction on the venous side, as opposed to the vascular alterations in HC, which are on the arterial side.

Patients with a particular, steroid-sensitive headache and often characteristic pathology at orbital phlebography, have been suggested to suffer from venous vasculitis. Fifty such patients were examined with computed tomography (CT) of the brain. The findings were compared with those of an age-matched reference group selected at random to represent normal subjects. The CT examinations were analyzed with respect to size of lateral ventricles and signs of atrophy. In both groups, there was a significant increase of atrophy with age. There was also a significantly higher degree of atrophy in the patient group as compared with the reference group. The findings indicate that the supposedly underlying venous vasculitis is related to early aging and atrophy of the brain.

1. The axonal conduction velocity and the voluntary discharge properties of 120 short toe extensor motor units were studied in man. 2. Electromyographic techniques were used which permitted the identification of individual motor unit potentials after proximal and distal electrical nerve stimulation and during maximum voluntary effort. 3. The necessary selectivity of the e.m.g. recordings was achieved in two circumstances. In some subjects, previous motor nerve lesions distal to the point of stimulation had led to collateral sprouting with larger motor unit potentials. In other subjects an accessory deep peroneal nerve was present, so that lidocaine block of the main motor nerve left a small number of innervated motor units. 4. The axonal conduction velocities of the individual motor units ranged from 30 to 54 m/sec with most motor units between 35 and 45 m/sec. 5. Motor units which voluntarily could be driven continuously at frequencies below 10/sec had axonal conduction velocities between 30 and 45 m/sec. 6. Motor units which on voluntary drive responded only in high frequency bursts had axonal conduction velocities between 40 and 54 m/sec. 7. Motor units with intermediate voluntary discharge properties had intermediate axonal conduction velocities. 8. Thus a relationship was established between voluntary discharge properties and axonal conduction velocity.

Orbital phlebography has been reported to be pathologic in some patients with Tolosa-Hunt's syndrome (recurrent painful ophthalmoplegia). A systematic study of the phlebographic findings in Tolosa-Hunt's syndrome in comparison with a normal material seems not to have been performed. In this investigation, orbital phlebography was performed in 19 patients with Tolosa-Hunt's syndrome and in a reference group of 23 persons without the disease. In 13 of 19 patients (68%) with Tolosa-Hunt's syndrome, the phlebography was pathologic (narrowing or occlusion of particularly the third segment of the superior ophthalmic vein, partial occlusion of the cavernous sinus). Orbital phlebography was normal in all but one of the subjects in the reference group. The medical history of this subject in retrospect revealed symptoms other than painful ophthalmoplegia commonly found in patients with Tolosa-Hunt' syndrome, suggesting that he suffered from a variant of the disease causing the syndrome. In one patient with recurrent painful ophthalmoplegia a biopsy from an eye muscle showed venous vasculitis, probably indicating the basic pathology behind the phlebographic changes in patients with Tolosa-Hunt's syndrome.

Eleven patients with episodic cluster headache in period, five patients out of period and six controls were studied concerning the effects of an increase of the intracranial blood volume by tilting. Common carotid artery (CCA) blood flow was similar in all three groups at baseline and during tilting. CCA diameters were similar at baseline and increased during tilting in all three groups, indicating that tilting caused an increase in the extra- and intracranial blood volume. Unilateral pain or sympathetic dysfunction did not appear during tilting in the patients out of period or in the controls. In four of eight studied patients with cluster headache in period, unilateral miosis and ptosis appeared during tilting. Two of these four patients developed intense unilateral pain, while the other two did not report any pain. Four other patients developed slight unilateral pain but no sympathetic dysfunction during tilting.

1. The discharge properties of individual motor units in different modes of voluntary contraction were studied with electromyographic techniques in the short toe extensor muscle of normal man. 2. The short toe extensor muscle consisted of type I and type II muscle fibres in about equal proportion. In some subjects there was type‐grouping so that recordings with sufficient selectivity could easily be obtained. 3. Certain motor units could be driven continuously, attained regular firing intervals even at a firing rate of 10/sec, increased slowly in firing rate with increase in contraction strength, had maximum firing rate below 30/sec during sustained contraction but above 60/sec in twitch contraction. 4. Other motor units could not be dirven continuously, did not fire repeatedly at rates below 20/sec, increased rapidly in firing rate with increase in contraction strength and attained firing rates above 100/sec. 5. There were intermediate forms between continuously firing low frequency motor units and intermittently firing high frequency motor units. 6. In a prolonged contraction of constant strength only continuously firing motor units were active. 7. On rapid accelerations, however, both continuously and intermittently firing motor units were active and played about the same role. 8. This applied also to prolonged series of accelerations as in rhythmically alternating movements. 9. In twitch contractions selective activation of intermittently firing motor units occurred if the muscle was relaxed prior to the twitch and great effort was used to elicit the twitch and minimum duration of the twitch was intended. 10. It is suggested that continuously firing low frequency motor units have type I muscle fibres and intermittently firing high frequency units have type II muscle fibres and that the order of recruitment and the relative roles of the two motor unit types are adapted to the mode of contraction.

1. The contraction time and the voluntary discharge properties of forty‐five short toe extensor motor units were studied in man. 2. The contraction time of the individual motor unit was studied by using selective electrical nerve stimulation or by averaging the increase in force related to its electromyographic potential in tonic voluntary contraction. 3. Both methods showed a range of contraction times from 40 to 90 ms. 4. The discharge properties of the individual motor unit were studied with e.m.g. techniques, permitting the identification of its potentials during maximum voluntary effort. 5. A motor unit which could be driven continously and had a minimum rate of about 10/s and a maximum rate of about 30/s had a contraction time between 60 and 90 ms. 6. A motor unit which could not be driven continously and had a minimum rate of about 20/s and a maximum rate above 40/s had a contraction time between 40 and 55 ms. 7. A motor unit with intermediate voluntary discharge properties had an intermediate contraction time. 8. It is concluded that each motor unit fires at its fusion frequency in voluntary contraction and that the voluntary discharge frequency range of a motor unit can be used as an indication of its contraction time.

Patients with a particular, steroid-sensitive headache and often characteristic pathology at orbital phlebography, have been suggested to suffer from venous vasculitis. Fifty such patients were examined with computed tomography (CT) of the brain. The findings were compared with those of an age-matched reference group selected at random to represent normal subjects. The CT examinations were analyzed with respect to size of lateral ventricles and signs of atrophy. In both groups, there was a significant increase of atrophy with age. There was also a significantly higher degree of atrophy in the patient group as compared with the reference group. The findings indicate that the supposedly underlying venous vasculitis is related to early aging and atrophy of the brain.

Thirteen consecutive patients with subacute unilateral loss of vision and periorbital pain but without pathology of the fundus or increased erythrocyte sedimentation rate, were investigated with visual evoked response, electrophoresis of serum and cerebrospinal fluid, and orbital phlebography. Seven of these patients were found to suffer from multiple sclerosis. The remaining 6 were considered to have venous vasculitis. There was a spontaneous recovery from visual impairment in all patients with multiple sclerosis, but not in patients with venous vasculitis. Of the latter patients, only two, who were treated with steroids within the first four days after onset of symptoms, regained vision. It appears that orbital phlebography is the diagnostic procedure of choice for proper management of patients with subacute loss of vision.

Thirteen consecutive patients with subacute unilateral loss of vision and periorbital pain but without pathology of the fundus or increased erythrocyte sedimentation rate, were investigated with visual evoked response, electrophoresis of serum and cerebrospinal fluid, and orbital phlebography. Seven of these patients were found to suffer from multiple sclerosis. the remaining 6 were considered to have venous vasculitis. There was a spontaneous recovery from visual impairment in all patients with multiple sclerosis, but not in patients with venous vasculitis. of the latter patients, only two, who were treated with steroids within the first four days after onset of symptoms, regained vision. It appears that orbital phlebography is the diagnostic procedure of choice for proper management of patients with subacute loss of vision