Object Considerable overlap exists in nerve root innervation of various muscles. Knowledge of myotomal innervation is essential for the interpretation of neurological examination findings and neurosurgical decision-making. Previous studies relied on cadaveric dissections, animal studies, and cases with anomalous anatomy. This study investigates the myotomal innervation patterns of cervical and lumbar nerve roots through in vivo stimulation during surgeries for spinal decompression. Methods Patients undergoing cervical and lumbar surgeries in which nerve roots were exposed in the normal course of surgery were included in the study. Electromyography electrodes were placed in the muscle groups that are generally accepted to be innervated by the roots under study. These locations included levels above and below the spinal levels undergoing decompression. After decompression, a unipolar neural stimulator probe was placed directly on the nerve root sleeve and constant current stimulation in increments of 0.1 mA was performed. Current was raised until at least a 100 μV amplitude–triggered electromyographic response was noted in 1 or more muscles. All muscles that responded were recorded. Results A total of 2295 nerve root locations in 129 patients (mean age 57 ± 15 years, 47 female [36%]) were stimulated, and 1589 stimulations met quality criteria and were analyzed. Four hundred ninety-five stimulations were performed on roots contributing to the cervical and brachial plexus from C-3 to T-1 (31.2%), and 1094 (68.8%) were roots in the lumbosacral plexus between L-1 and S-2. The authors were able to construct a statistical map of the contributions of each cervical and lumbosacral nerve root for the set of muscle groups monitored in the protocol. In many cases the range of muscles innervated by a specific root was broader than previously described in textbooks. Conclusions This is the largest data set of direct intraoperative nerve root stimulations during decompressive surgery, demonstrating the relative contribution of root-level motor input to various muscle groups. Compared with classic neuroanatomy, a significant number of roots innervate a broader range of muscles than expected, which may account for the variability of presentation between patients with identical number and location of compressed roots.

Arteriovenous malformations (AVM's) of the spine commonly cause progressive myelopathy. Occasionally, myelography reveals serpentine filling defects characteristic of a spinal AVM, but an AVM or arteriovenous (AV) fistula cannot be demonstrated arteriographically, despite selective catheterization of all vessels known to have the potential of supplying the spinal cord and spinal dura. Often, and particularly in the setting of subacute or acute deterioration, this has been attributed to spontaneous thrombosis of the veins (the Foix-Alajouanine syndrome). Three patients are reported in whom intracranial dural AV fistulas, supplied by branches of the internal and external carotid arteries, drained into spinal veins and produced myelopathy. In one patient, motor and sensory deficits were limited to the lower extremities. In all three patients, disconnection of the fistula from its spinal venous drainage permitted arrest of a rapidly progressive myelopathy and partial recovery. These findings indicate that some patients who appear to have spinal cord AVM's but exhibit negative spinal arteriography are suffering from cranial dural AV fistulas and therefore need carotid as well as spinal arteriography. The considerable distance of these fistulas from the level of neurological expression supports venous hypertension as a pathophysiological mechanism of spinal cord injury. Interruption of a cranial dural fistula draining into spinal veins permits recovery of the myelopathy.

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We have correlated the tectal connections and cytoarchitecture of regions in the rabbit's midbrain and caudal thalamus. The inferior colliculus projects ipsilaterally to the central gray, superior colliculus, and via the brachium of the inferior colliculus to its interstitial nucleus and the parabrachial region of the midbrain tegmcntum. From the brachium, fibers fan out to the principal and internal divisions of the mcdial geniculate. A smaller contralateral pathway sweeps into the contralateral inferior colliculus and in its brachium to the interstitial nucleus, the parabrachial region, and the intcrnal and principal divisions of the medial geniculate.The superior collicular projection is mainly ipsilateral. Medially, fibers terminate in the central gray and pretectal area. Laterally, fibers ascend in the superior brachium to parabrachial region, suprageniculate pretectal nucleus, posterior complex, caudodorsal internal division of the medial geniculate, and to a discrete part of the ventral nucleus of lateral geniculatc. A component of the commissure of Gudden originates in the rostra1 superior colliculus and terminates in the contralateral ventral lateral geniculate, posterior complex, pretectal area and midbrain tegmentum.Interconnections between the colliculi and overlap of their projections in the parabrachial region, the central gray, and the internal division of the medial geniculate are described.We have undertaken to determine precisely the terminal distribution of the ascending efferents o i the rabbit tectum and to correlate our findings with the morphological subdivisions of nuclear groups which receive these fibers. The boundaries of these nuclei in the midbrain and caudal thalamus are particularly distinct in the rabbit. Although i t is known that the rabbit inferior colliculus projects to the ventral part of the medial geniculate body (Jelenska-Macieszyna, '1 1; Moore and Tarlov, '63) and that the superior colliculus projects to the dorsal part of the medial geniculate body (Munzcr and Wiener, '02; Jelenska-Macieszyna, '1 1 ; Sekino, '59; Giolli, '61; Cragg, '62; Tarlov, '65); the exact distribution of the fibers ascending from the tectum to the midbrain and posterior thalamus has not previously been described. We have reviewed the pertinent literature elsewhere (Tarlov, '64). MATERIALS AND METHODSTectal lesions i n the brains of 25 adult male albino rabbits were made with a suction pipette through a small occipital craniectomy. After postoperative periods ranging from 4 to 10 days for inferior colliculus J. COMP. NEUR., 126: 403-422. lesions and from 3 to 34 days for superior colliculus lesions, the animals were perfused with warm gum acacia-dichromateformol salinc solution according to the method of Rasmussen ('63). Ten to twelve hours later the brains were removed. After five days serial frozen sections were cut frontally or horizontally at 35 p. One series of sections was stained by a modification of the Nauta-Gygax technique (Nauta, '57) and a n adjacent series with cresyl violet. In...

Papillary tumors of the temporal bone have been recognized recently as an aggressive skull base neoplasm. Their progression is silent, typically manifested only after widespread local destruction has occurred. The sites of origin and potential for malignant behavior are controversial.':" Numerous case reports have consistently demonstrated destruction of the otic capsule and early invasion of the posterior fossa. These lesions were usually identified as middle ear adenomas, papillary cystadenomas, or papillary adenocarcinomas. They have been differentiated from the more indolent middle ear adenomas by their propensity for erosion of petrous bone and extensive intracranial extension. 7 ,8,w -12 Heffner" recently studied the ultrastructural histology of these tumors and proposed that the endolymphatic sac may be the true site of origin.We previously reported two patients with von Hippel-Lindau disease and papillary tumors of the temporal bone.":" The tumors were bilateral in the first patient. We have subsequently observed the development of a new contralateral lesion in our second patient. Early identification of this tumor enabled us to study its growth and ultimately to excise the lesion, which was clearly arising in the endolymphatic sac.Primary tumors of the inner ear have rarely been reported, and further research is needed to understand the development and behavior of such neoplasms.