13Adult Neurosurgery
A Colloid cyst
Colloid cysts represent 0.5 to 2% of all brain tumors and occur in the anterior part of the third ventricle near the foramen of Monro. These lesions can be associated with the development of hydrocephalus and rapid clinical deterioration. Sudden death has been reported but is rare, and likely involves the colloid cyst acting as a ball valve and suddenly shifting and occluding cerebrospinal fluid outflow.
A Burning pain, autonomic dysfunction, and trophic changes following obvious nerve damage
Complex regional pain syndrome (CRPS) type 2 follows nerve injury and originally was described following high-velocity missile injuries. CRPS type 1 (also known as reflex sympathetic dystrophy) is similar to CRPS type 2 in symptoms but does not demonstrate obvious nerve damage. (B) Increased perspiration in excess of what is required for regulation of body temperature suggests hyperhidrosis. (C) CRPS type 2 requires nerve damage for the diagnosis. (D) Dejerine-Roussy syndrome follows a thalamic stroke and is characterized by an initial lack of sensation and tingling on one side of the body followed later by severe, chronic dysesthesias or allodynia. (E) Munchausen syndrome is characterized by recurrent hospitalizations with dramatic, untrue, and extremely improbable tales of past experiences.
C Intraventricular hemorrhage (IVH), position of ICH, patient age
The intracranial hemorrhage (ICH) score is calculated from four factors: Glasgow Coma Scale (GCS) score, ICH volume, whether or not the ICH is infratentorial, and patient age. A GCS score of 3–4 yields two points, 5–12 yields one point, and 13–15 yields no points. One point is given to an ICH at least 30 cm3 in size, and an additional point is given to an ICH with an infratentorial origin. Finally, one point is given if the patient is at least 80 years old. The ICH score thus ranges from 0 to 6.
C Obtain blood cultures
The likely diagnosis is diskitis, and the next step is to obtain blood cultures to confirm the hematogenous source and obtain an organism to treat. If blood cultures are negative, guided needle biopsy of the disk space should be done. Obtaining a serum erythrocyte sedimentation rate and C-reactive protein concentration also can be helpful. (A) A lumbar puncture is contraindicated due to the possibility of seeding the intrathecal space with an infectious agent.
A Improves with activity
Although some patients with severe back pain and muscle spasms may improve with no more than 48 hours of bed rest, patients with mild to moderate back pain should return to near-normal work schedules and have improvement in back pain with activity, as this increases flexibility.
C Through the bulk of the psoas major
The transpsoas approach to the lumbar spine places the entire lumbosacral plexus at risk for injury. The risk can be minimized by staying in the bulk of the psoas major muscle and with close neuromonitoring.
C Ocular neuromyotonia
Although rare, ocular neuromyotonia can occur after skull base radiation, with a reported mean time of 3.5 years following radiation. It is characterized by episodic, tonic contractions of one or more extraocular muscles, resulting in episodic diplopia. Varying success has been reported with membrane stabilizing agents (antiepileptics) or strabismus surgery.
E L5 nerve root and common peroneal nerve at the fibular head
This patient has an injury to the L5 nerve root and the common peroneal nerve as explained. The peroneal nerve must be affected after it has given off its motor innervation to the short head of the biceps femoris, as this muscle is unaffected. The common peroneal nerve is most commonly injured as it crosses the fibular head, resulting in the symptoms seen in this clinical scenario. The fibrillations present on electromyography can indicate an axonal injury and uncontrolled and spontaneous firing of muscle cells. Present but reduced motor unit potentials indicate reduced motor unit recruitment and can indicate impeded nerve conduction. (A) With an L4 nerve root abnormality, abnormalities of the tibialis anterior would be expected. (B) An L5 nerve root abnormality explains the abnormalities in the extensor digitorum longus and gluteus medius but fails to address the abnormalities seen in the common peroneal nerve. Abnormalities in the gluteus minimus also would be seen with an L5 nerve root abnormality. (C) The S1 nerve root innervates the peroneus longus and brevis. (D) The common peroneal nerve supplies the short head of the biceps femoris before passing around the fibular head and branching into a superficial and deep branch. The superficial branch supplies motor innervations to the muscles of the lateral compartment of the leg (the peroneus longus and brevis, which evert the foot) along with sensory innervation to the lateral leg. The deep branch supplies motor innervation to the muscles of the anterior compartment of the leg (the tibialis anterior, extensor hallucis longus, extensor digitorum longus, and peroneus tertius) along with muscles in the foot. It supplies sensory innervation to the dorsum of the foot in the first web space.
D Lungs
When malignant peripheral nerve sheath tumors (MPNSTs) are discovered, a chest CT (fine cut) should be ordered to look for metastatic disease, as this is the most common location of metastatic spread. (E) Metastases of MPNSTs rarely occur in locations like the lymph nodes or the heart.
A Dural
The American/English/French arteriovenous malformation (AVM) classification divides spinal vascular malformations into four types. Type 1 (dural AVM) is the most common; a radicular artery feeds into an engorged spinal vein along the posterior cord. This type is low flow. Type 2 (spinal glomus AVM) is a true AVM of the spinal cord. Type 3 (juvenile spinal AVM) is an enlarged glomus AVM that occupies the entire cross section of the cord and invades the vertebral body. This type may cause scoliosis. Type 4 (perimedullary AVM) forms a direct fistula between arteries supplying the spinal cord and draining veins. (C) Extramedullary/intradural is not an AVM type and instead refers to an anatomic location typically used when describing spinal neoplasms.
A Microvascular decompression
Although multiple sclerosis patients have a poorer response than patients without the disease to any treatment for trigeminal neuralgia, patients with multiple sclerosis respond very poorly to microvascular decompression.
D Diplopia
Diplopia can occur following a stereotactic mesencephalotomy secondary to lesioning near the inferior colliculus. The diplopia is due to a defect in vertical eye movements and often resolves. (A) No motor tracts are encountered during a stereotactic mesencephalotomy. Weakness in the extremities is more likely to occur during a cordotomy.
C 75%
Although the definition of serviceable hearing varies, most sources require a speech discrimination score of at least 50 to 70%. For preoperative counseling, a speech discrimination score under 75% significantly raises the risk of not having serviceable hearing following a vestibular schwannoma resection.
E Preparation for transsphenoidal decompression immediately
The patient displays symptoms of pituitary apoplexy caused by a rapid expansion of her known pituitary adenoma secondary to necrosis or hemorrhage. This can lead to headache, nausea, somnolence, and other neurologic changes due to elevations in intracranial pressure along with exacerbated visual field cuts and ophthalmoplegia due to local mass effect. Treatment is emergent decompression of the sella turcica and pituitary lesion. Immediate administration of a stress dose of steroids also is important. Subarachnoid hemorrhage can be seen with pituitary apoplexy, and an angiogram can be useful to rule out an aneurysm as a cause. (A) The patient likely is not having a migraine due to the new ophthalmoplegia with a known pituitary tumor. (B, D) This patient needs treatment soon to avoid permanent ophthalmic injury and neurologic damage associated with elevated intracranial pressures. (C) Lab work is unlikely to aid in the treatment of this patient as the pituitary lesion is unlikely to have grown suddenly. Outpatient lab work and waiting for inpatient labs to return will not affect the need for definitive treatment.
C 4
House-Brackmann facial nerve function classification grading ranges from 1 (normal) to 6 (total paralysis). Grade 2 is mild dysfunction. Grade 3 is obvious but not disfiguring facial asymmetry. Grade 4 dysfunction entails the inability to close the eye. Grade 5 is barely perceptible motion.
E No form of nicotine avoids the risk of decreased spinal fusion rates.
Nicotine in all its forms has been shown to affect adversely spinal fusion rates.
B 8 in-lbs
(E) The recommended torque for the screws on many halo vests is 30 in-lbs.
B Hemiballism
Hemiballism is a unilateral, involuntary jerking of the proximal limb due to a lesion of the suthalamic nucleus. (A) Myoclonus describes shock-like contractions that are irregular and asymmetric and can have numerous etiologies. (C) A pill-rolling tremor is characteristic of parkinsonism and pathology involving the substantia nigra pars compacta. (D) Dystonias leading to fixed limb postures may be due to putaminal destruction. (E) Chorea is seen in Huntington disease and is a result of striatum atrophy.
B Balance
Patients with Parkinson disease who have undergone deep brain stimulation surgery experience a brief period of improvement in balance followed by a return of balance difficulties. The procedure is more effective at reliving symptoms of dyskinesia, tremors, and rigidity.
A Paraspinal muscle fibrillations
Electromyography is not sensitive for radiculopathy; however, when it is abnormal, it is very specific. Paraspinal muscles are innervated by dorsal rami, which exit proximally to the dorsal root ganglion. Paraspinal muscle fibrillations can indicate irritation of these dorsal rami. (B) Sensory nerve action potentials (SNAPs) are normal in lesions proximal to the dorsal root ganglia; therefore, most disk herniations do not affect SNAPs. (C) Increased motor fiber recruitment indicates a myopathic process. (D) Spontaneous nerve activity (including positive sharp waves and fibrillation potentials) can be seen after denervation.
B Initiate a heparin drip if there are no contraindications
Blunt cerebrovascular injuries of the internal carotid artery are common following motor vehicle collisions and are thought to be related to neck hyperextension with lateral rotation. The injuries most often occur 2 cm from the origin of the internal carotid artery. The blunt cerebrovascular injury (BCVI) classification is as follows: grade 1, luminal irregularity with ≤ 25% stenosis; grade 2, luminal irregularity with > 25% stenosis or an intraluminal thrombus/raised intimal flap; grade 3, pseudoaneurysm; grade 4, complete occlusion; grade 5, transection with extravasation. The incidence of stroke increases with the grade. Although outcomes are not entirely known, the data suggest that anticoagulation may reduce the risk of injury progression with grade 1 injuries.
C Midcervical spine fractures
Because of “snaking,” which may occur between the halo fixation points and the vest, a halo brace is best suited for upper and lower cervical spinal fractures but is poor at maintaining distraction.
B Anterior inferior cerebellar artery
The anterior inferior cerebellar artery can compress cranial nerve VII to produce hemifacial spasm. (A) The posterior inferior cerebellar artery is associated with glossopharyngeal neuralgia. (C) The superior cerebellar artery is associated with trigeminal neuralgia.
C 1.4
In clinical studies, an INR of 1.4 is considered safe for performing a percutaneous needle liver biopsy. Extrapolated from this, an INR of 1.4 is considered safe for performing neurosurgical procedures. The prothrombin time should be 13.5 seconds or less.
B Postfixed chiasm
A pituitary tumor with a postfixed chiasm (located posterior to its normal position over the dorsum sellae) has an increased likelihood of compressing the optic nerves and causing a “pie in the sky” deficit (superotemporal quadrantanopsia) through compression of the knee of Wilbrand. Postfixed chiasms also can result in chiasmatic compression and a bitemporal hemianopsia. (A) A prefixed chiasm (located anterior to its normal position over the tuberculum sellae) is associated with optic tract compression and a homonymous hemianopsia. (C, D) The optic chiasm normally lies superior to the sella turcica.
D Pure tone audiogram of 40 dB or less; speech discrimination score of at least 60%
Hearing is considered serviceable if the pure tone audiogram is less than or equal to 50 dB and speech discrimination is 50% of more (the “50/50” rule). American Academy of Otolaryngology-Head and Neck Surgery classifications A (30/70) and B (50/50) are considered serviceable and preservable.
A Rapid administration of corticosteroids
Pituitary apoplexy can be considered a surgical emergency if it is rapidly progressive. In addition, given the compromise of the pituitary gland, prompt treatment with corticosteroids is necessary. (B, C) The rapid onset of a headache may suggest an aneurysmal subarachnoid hemorrhage aneurysm, and a posterior communicating artery aneurysm may produce a cranial nerve III palsy. Subarachnoid hemorrhage is not associated with bitemporal hemianopsia, however. (D) Cavernouscarotid fistulae often are associated with a pulsatile proptosis. Infectious etiologies (e.g., Tolosa-Hunt and Gradenigo syndromes) often include a painful ophthalmoplegia. (E) Increased intracranial pressure and uncal herniation could produce a cranial nerve III palsy, but bitemporal hemianopsia in an awake patient likely would not occur.
D D
The American Spinal Injury Association (ASIA) impairment scale indicates the completeness of a spinal cord injury and is different from the ASIA motor scale. ASIA A represents a complete injury without motor or sensory function below the injury level. ASIA E represents normal motor and sensory function. ASIA B is an incomplete injury with preservation of sensory but not motor function below the level of injury. ASIA C is an incomplete injury with preservation of motor function in at least half of the key muscles below the level of injury graded at less than 3/5, whereas, in ASIA D, half of the key muscles below the level of injury have at least 3/5 strength. Of note, sensory preservation requires that the S4 and S5 segments also be intact. The ASIA impairment scale only applies to patients who have sustained spinal cord injuries and should not be used to describe a neurologic exam otherwise.
B Anterior cord syndrome
Anterior cord syndrome (anterior spinal artery syndrome) presents with paraplegia and dissociated sensory loss, with loss of pain and temperature sensation but with preservation of posterior column function (positional and fine touch sensation). It can result from an infarct involving the anterior spinal artery. (A) Central cord syndrome presents with a greater motor deficit in the upper extremities relative to the lower extremities. It often results from a hyperextension injury in the presence of degenerative osteophytes. The overall prognosis is that half of affected patients eventually will be able to ambulate independently. (C) Brown-Séquard syndrome presents with dissociated sensory loss (loss of pain and temperature sensation with preserved light touch sensation), with ipsilateral paresis and posterior column dysfunction. Of the listed syndromes, Brown-Séquard syndrome has the best prognosis, with 90% of affected patients regaining ambulatory status. (D) Posterior cord syndrome is rare. Symptoms include pain and paresthesias with minimal long tract findings. (E) Cauda equina syndrome is compressions of the cauda equina (not the spinal cord), resulting in urinary retention, saddle anesthesia, motor weakness, and low back pain due to the involvement of multiple nerve roots.
A Superior and medial
The pars interarticularis and pedicle of the C2 vertebral body, from posterior to anterior, are oriented superiorly and medially. The entry point for C2 pedicle screw placement is 3 to 4 mm superior to the inferior margin of the C2 inferior facet and at the midpoint mediolaterally with a trajectory of 20 to 30 degrees medially and 25 degrees superiorly. The vertebral artery courses laterally as it passes through the C2 transverse foramen so that the more superior the screw is placed, the farther away from the vertebral artery the screw is located.
E Barrel chest
Relative contraindications for odontoid screw placement include a type 3 odontoid fracture, large fracture gaps, irreducible fractures, chronic fractures, pathological fractures, and fracture lines that are oblique to the frontal plane. Odontoid screws are useful for acute, type 2 fractures with intact ligaments but can be difficult to place in patients with short, thick necks or barrel chests. This relative contraindication sometimes can be circumvented with appropriate instrumentation. (B) The most significant absolute contraindication for odontoid screw placement is the disruption of the transverse atlantal ligament as seen on MRI or indirectly if the sum of the overhang of the lateral masses of C1 on C2 exceeds 7 mm. This latter assessment is known as the rule of Spence.
D Teardrop fracture
Teardrop fractures are compression/flexion injuries that often are unstable. They usually present with chip fractures and retrolisthesis, sagittally oriented fractures, a kyphotic deformity, facet/disk space disruption, and soft tissue swelling. (A) Avulsion fractures present with chip fractures as a result of anterior longitudinal ligament traction on the fractured bone (a hyperextension injury). There often is no misalignment, body fracture, or posterior element or disk disruption. (B) A clay-shoveler fracture is an avulsion of the C7 spinous process. (C) Jefferson fractures are four-point burst fractures of the C1 ring. They are classified as unstable but often are treated with orthosis; they typically present without neurologic deficits. (E) Locked facets result from distraction/flexion injuries and often present with anterolisthesis.
B Distracting pedicle screws to reduce indirectly the retropulsed segment by putting tension on the posterior longitudinal ligament
Ligamentotaxis is the theory for the practice that is used by some physicians to “pull” bony fragments that are in the central canal back to their normal positions (assuming the posterior longitudinal ligament is intact). Typically, this technique is used with a distraction technique such as with pedicle screws. (A, C–E) These techniques are utilized in deformity and spinal trauma surgery but are not considered ligamentotaxis.
B Zone 2
Sacral zone 2 fractures occur vertically, ascend the sacral foramina, and may cause unilateral L5, S1, or S2 root injuries (including sciatica). (A) Sacral zone 1 fractures occur at the sacral ala and may be associated with an L5 root injury. (C) Sacral zone 3 fractures occur within the sacral canal and can cause sphincter dysfunction with bilateral nerve root injuries and saddle anesthesia. Fractures extending vertically in zone 3 are associated with pelvic ring fractures. (D) Transverse sacral fractures sometimes are classified as zone 4 injuries and occur from falls. They can produce severe neurologic deficits. (E) There is no zone 5.
A Greater than 1 mm of blood
The Fisher grading system is effective in determining the risk of vasospasm associated with aneurysmal subarachnoid hemorrhage according to the amount of blood seen on CT. Grade 1 is without subarachnoid hemorrhage. Grade 2 indicates subarachnoid hemorrhage less than 1 mm in thickness. Grade 3 indicates a localized clot or layer of subarachnoid hemorrhage at least 1 mm in thickness. (C) Grade 4 indicates intraparenchymal or intraventricular hemorrhage.
D Anterior communicating artery
Anterior communicating artery aneurysms often present with blood in the anterior interhemispheric fissure, a hematoma in the gyrus rectus, and intraventricular hemorrhage in the third ventricle, which is thought to reach the ventricles through the lamina terminalis.
C Antibiotics and serial imaging
Mycotic aneurysms are common in bacterial endocarditis and occur in 3 to 15% of patients with this diagnosis. The aneurysms are found most commonly in the distal middle cerebral artery branches. At least 20% of patients have multiple aneurysms, and there is an association with immunocompromised and intravenous drug abuse patients. Treatment consists of antibiotic therapy, as these aneurysms are friable and not easily amenable to surgical or endovascular treatments. Serial angiograms are used to follow the resolution of mycotic aneurysms. Surgical clipping may be indicated in patients with subarachnoid hemorrhage, increasing aneurysm size despite antibiotic treatment, failure of antibiotics to resolve the aneurysm, and focal deficits.
C Brachytherapy has no role as an adjuvant to whole brain radiation
Brachytherapy provides no significant overall survival or quality-of-life benefits when compared with whole brain radiation and should not be used alone or as an adjuvant therapy for high-grade gliomas. This is due to the diffuse nature of gliomas and the side effects of brachytherapy.
A Intravenous chemotherapy
Following resection of a low-grade oligodendroglioma, chemotherapy is the mainstay of adjuvant therapy, with radiation reserved for higher grade lesions due to their aggressiveness and more diffuse characteristics. The typical chemotherapy protocol of procarbazine, CCNU, and vincristine is given intravenously and not intrathecally.
C 25 to 40%
Complications rates are high when shunting patients with normal pressure hydrocephalus, likely in part due to the advanced average age of the patients with the condition. Complications include subdural hematomas, shunt infections, intracranial hemorrhages, seizures, and shunt malfunctions. As for the symptoms of normal pressure hydrocephalus, incontinence followed by gait abnormalities is the symptom most likely to improve with shunting. Dementia is the symptom least likely to improve.
C Presence of a Martin-Gruber anastomosis
A Martin-Gruber median to ulnar nerve anastomosis occurs in 15 to 30% of individuals and consists of a communicating nerve branch between median and ulnar nerves. A clue to the presence of a Martin-Gruber anastomosis with carpal tunnel syndrome is a faster than expected conduction velocity in the median nerve in the forearm. In severe carpal tunnel syndrome, because nerve fibers are passing around the carpal ligament through the ulnar nerve, antecubital fossa stimulation may result in thenar stimulation faster than with stimulation at the wrist (there also will be a positive deflection). (D) Marinacci syndrome is a “reverse” Martin-Gruber anastomosis characterized by an ulnar to median nerve anastomosis that can cause carpal tunnel syndrome from an ulnar nerve compression at the elbow.
A Radiographs are not indicated
There are five NEXUS criteria to indicate the need for cervical spine imaging: midline cervical tenderness, focal neurologic deficits, altered level of consciousness, intoxication, and painful distracting injuries. If these are all negative, radiographic studies are not indicated. In trauma patients who are symptomatic, obtunded, or have an unreliable neurologic exam, a thin-cut axial CT scan is indicated with reconstructions.
D Admit to the floor, obtain blood cultures, and consult interventional radiology for biopsy of the psoas abscess prior to administering antibiotics (if the biopsy can be done in a timely manner)
Medical management of patients with epidural abscesses is preferred when there are long-standing symptoms without progressive neurologic deficits, when imaging is not worrisome for severe compression, in patients with prohibitive operative risk factors, and in patients with complete paralysis for longer than 3 days. Epidural biopsy is not recommended; however, disk space/vertebral body biopsy is a reasonable option.
A Absence of atypical pain
Absence of atypical pain is a favorable prognosticator in surgical and radiosurgical candidates for trigeminal neuralgia treatment. Other favorable factors include using higher radiation doses, a lack of previous trigeminal neuralgia operations, and normal pretreatment sensory function.
C Cranial nerve IX rhizotomy with sectioning the upper one third of cranial nerve X
When an offending vessel (classically the posterior inferior cerebellar artery) is seen compressing cranial nerve IX, microvascular decompression (MVD) is the preferred treatment choice. During an exploration that fails to reveal vascular compression of the nerve, the most effective treatment includes sectioning of cranial nerve IX and the upper rootlets of cranial nerve X. Studies suggested that there is a higher rate of pain recurrence when both nerves are not sectioned simultaneously. The risks of sectioning cranial nerve X may include significant bradycardia, dysphagia, and voice hoarseness.
B Isthmic
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